I, Personally, am a big fan of the underrated Apparatus of Kwalish. Don't know why, but I am. When Roland St. Jude mentioned the Library could be mobile, this idea popped into my head. Anyway, here's my library.

The Library of Kwalish

Made by Kwalish, a bookwormy, paranoid, Lobster-obsessed gnome wizard with a knack for invention, this enormous Library includes 2 guest rooms, a Pocket Dimension, and a Cockpit. In its most basic form, the Building appears to be a Collosal (40 by 100 foot) iron barrel, with a closed (and, if further examined, unopenable) door high above the ground on one end (the back end). After the activation of various levers in Control Room, the following results can be achieved (or deactivated if already deployed):
1. Extend the Legs (which are six to a side, angular, and fold out of the Barrel's sides) which allow mobility at a speed of up to 50 feet per round.
2. Extend the Tail, which can serve as a defensive covering for the door, be used to provide a swim speed of 25 feet per round, or 50 with the legs extended and swimming as well.
3. Open the Cockpit shutters and/or extend the Cockpit, allowing visibility from the Pilot Room in a 90 degree arc if not extended or 180 degree arc if extended. The pilot(s) are protected by a Glassteel window.
4. Open the roof shutters, which normally cover a similar Glassteel window.
5. Extend one or both of the Pincers.
6. Attack with Pincers.
7. Extend the "feelers" which can be extended to reach the ground of use as exits.
8. Reveal the Ballistae, which rise out building, one on each shoulder.
9. Move. Reveal one or both "eyes" which rise out of the top between the two Ballistae. They project out light in a 60 foot cone.
10. Open the rear door.
11. Activate the Alarm, causing the guardians to attack anyone they see other than Kwalish.
The following is a summation of its characteristics: hp 2,000; hardness 30, spd 50 ft swim 50 ft; AC 25 attack -3, or +4 if the pilot has taken the Fortress Pilot feat, 2 pincers 2d20+16 damage, or -10 of pilot or +10 if they have taken the Library Pilot feat, 2 Ballistae, same target, 2d12+13. The Library has enough air in it to let someone survive in it for 12 hours underwater or in a vacuum. Visitors halve the duration for every visitor. Overwhelming Evocation and Transmutation, CL 25th, Craft Wondrous Item, Animate Objects, Continual Flame, Levitate, creator must have 15 ranks in the Knowledge (Engineering and Architecture) skill. Price 200,000 gp, Weight 6,000 pounds.
As anyone with even the faintest idea of what the Apparatus of Kwalish is has probably figured out, the Library is essentially just an over sized Apparatus. A break down of the interior is located here:
Cockpit: This 15-15 orbicular room is source of the entire Library's controls. When the Cockpit shutters are closed, it is lit by a bright lantern hung from the ceiling. The front of the room is taken up by a control panel with room for up to 4 Small or 3 Medium pilots to effectively work. The machine is incredibly complex, and it takes someone without the Library Pilot feat 2 rounds to activate any of the effects above. There is also a 20 percent chance they will activate one of the other effects, determined by rolling a d10. The Library Pilot feat is:
Library Pilot (general)
Prerequisites: 7+ ranks in Knowledge (Engineering and Architecture), must have read the instruction guide to the Library of Kwalish.
Effect: You take only 1 round to activate one of the Library's effects, and do so without fail. You also get bonus's on attacks with the Library's weaponry, due to being able to effectively use the magical targeting array.
Normal: You take 2 rounds to activate an effect, and might use the wrong one. You take penalties on attacks with the Library's weaponry due to the unfamiliar targeting array.
Library: The main body of the ship, the Library is 30 ft by 60 ft long. It is lit by 3 Ornate Chandeliers when the roof shutters are closed. Both long walls are book cases, and the room is divided by a central bookcase with various openings to get through. The library is small, but is one of the greatest centers of Architectural and Engineering Knowledge. The list of books is given below. The room is guarded by 4 automated Apparatus of Kwalish's, who are instructed not to . The statistics for these are: hp 200, hardness 15, spd 20, swim 20, AC 20, atk +12 2d8 melee 2 pincers. Strong Evocation and Transmutation, CL 19th, Craft Wondrous Item, Animate Objects, Continual Flame, Creator must have 8+ ranks in Knowledge (Engineering and Architecture), Price: 90,000 gp weight 500 pounds.
Guest Quarters: These two 10-10 Cabins are located in the back of the Library, one on each side (their dimensions are not included in the figure above. i.e. the actual room is 30-70) they are uncomfortable, with a narrow bed and a small table with two chairs. Kwalish doesn't use these rooms, they are entirely for his rare guests (Kwalish lives instead in an opulent Pocket Dimension underneath a trapdoor located between the two rooms he created with the Dimensional Codex, which also contains a large workshop where he services his Apparatus's and generally tinkers around).
Guest Lock: The door on the back has an Extendable ramp which can be lowered and the door opened from outside this room. Someone coming up the ramp finds themselves in this bare 10 foot square room with a door that has a (glassteel) porthole, and a periscopic device, which is actually a speaker. Kwalish uses this to converse with anybody looking to gain entrance to his Library. Most applicants are turned away gently with increasing force, but others are allowed on depending on Kwalish's whims.
Here is a list of the Library's Tomes, the linking factor being that they are all some form of book designed for use to someone building something.
Non-magical texts: Many of the books in the Central bookcase are non-magical in origin. The (nonmagical) pride of Kwalish's Library, However, is a book series called a Treatise on Architecture in Limbo, a very detailed (an entire shelf is taken up by it) series on how the Raw Chaos of Limbo (or a similar plane) effects Architecture, and how Githzerai Monasteries avoid this.
Magical Texts: The Right hand side of the Library is taken up by Kwalish's notes and blueprints on his Apparatus's and Library. The culmination of this is his own book, Designing and Building an Apparatus, is a detailed Book containing a step-by-step instruction set and explanation series for designing an Apparatus (automated or manual) or a Duplicate of the Library. One using the book gains 10 equivelant ranks in Knowledge (Engineering and Architecture), and the equivalent of the Craft Wondrous Item feat for the purposes of designing an Apparatus or Library duplicate. The back of the Book also serves as a spell book (no space remaining) and has the following spells: Continual Flame, Animate Objects, and Levitate.
3. Epic Text: one of Kwalish's favorite Books is the Dimensional Codex, essentially a Pocket Dimensions For Dummies book, which contains everything you need to know about the creation, use, and upkeep of a pocket dimension. Further, it allows a user create a Pocket Dimension. This effect can only be used once, and the dimension in question can be no bigger than 50 foot square. This is a permanent effect with a fixed portal location (although what the portal is fixed to can be mobile).
4. Artifact Text: on a dive some years back, Kwalish discovered a series of interlocking stone tablets that formed a writing that was totally alien yet he was able to understand perfectly. It explained how to create Elder Eidolons (see Lords of Madness, sorry), an Art long thought lost. Some believe that this text is what first caused Kwalish's fall into paranoia, seeing and understanding things that were not meant for mortals to understand. Regardless, Kwalish never allows it out of his Pocket Dimension, and has treated it with caring and almost reverence, unwilling for reasons even he doesn't know to put it's Eldritch secrets to use. The Apparatus's of Kwalish count as Guardians. The item, on the other hand, is an odd engine part Kwalish discovered a while ago, and still hasn't been able to figure out the use of yet (in reality it is a piece of engine from a Kolyarut Inevitable). He keeps it on a pedestal in one of the breaks in the central shelf. Oh yes, Kwalish is a Gnome Transmuter 25 with max ranks in Knowledge (Engineering and Architecture). I would have gone into more detail, but Iím cutting it close as it is.