In some ways, Eric and I over prepared for our move from land to sea, and I'd say that getting rid of our massive book collection was one such way. This isn't to suggest that we're upset by our decision (we're not)--it's just that Sea Gem has more book storage space than we anticipated (although not enough that we could have kept all of our books).
Eric and I keep the majority of our current modest book collection above our navigation station (we keep two smaller collections in both the aft and forward staterooms):
Helina's room has a small bookshelf, which is filled with her very own collection of tiny favorites:
So, despite our best efforts, plenty of books have made their way aboard the boat. To maintain balance, we'll rotate many of Helina's current collection off of the boat as new, age-appropriate books make their way aboard, and eventually we'll wean her off of real books and get her hooked on a Kindle (or whatever they have by the time she's ready for one). But don't worry, our new marina is just steps away from a library, so Helina (and Eric and I) will never be too far from actual books, should we ever want one.