This review will contain spoilers!
In many sentences:
Last Book is a quick, fun read. The highlight of it for me was the language that Philbrick develops. From the beginning there is a certain rhythm to all the new words that this futuristic world has, and they work really well. For example, when describing his initial meeting with Ryter, he says "[W]hatever, but I'm not there to flapjaw with some gummy old mope" (14). Even if you don't know what all these words mean at this point, you get the point, and this same effect is pulled off time and time again throughout the book. It's a consistent, thorough adjustment of certain elements and ideas in the language of the time and it works really well. I imagine the book would have felt rather dull and derivative if not for the new language that Philbrick employs.
The characters, while not the deepest, were also fun. The presence of Little Face was probably my favorite. He didn't say much, but the fact that he just wanted to be loved and to love others so much that he followed Spaz outside the latch was both heartbreaking and poignant. Even a child that had no parents or family to speak of would seek those things out.
My least favorite character was actually Ryter. Not because he was poorly developed, but because he just felt like a vehicle to get the "books are important" message across. While I agree with his point, it felt like he was preaching it to me, rather than allowing the story itself be that which convinces me that books and stories are important. Plus, I felt like this was written to "teach kids that books are really important" and, honestly, I don't think we need to convince kids of that. I think kids know that. And if they don't, a book that tells them that as explicitly as this one does won't convince them. The way to prove that books are important is to give them excellent books to read. Fortunately, I don't think this problem is devastating or disqualifies this from being an example of a good book, but I do think it could do some harm to its own point if it's given to a young reader who has a preconceived bias against reading.
Ultimately, the few minor flaws in Last Book are nowhere near enough for me to not recommend this book. In particular, I think readers who enjoy relatively tame post-apocalyptic adventures about courage and compassion will find a lot to like in this book.