This was an entertaining read that reminded me a bit of Cory Doctorow's Little Brother: although Robin Sloan's book is more of a literary mystery and less of a call to action against an increasingly intrusive government (OK, Penumbra isn't that at all), the attempts to reconcile old knowledge and new today strike a similar chord. As Sloan notes on his Web site, "This is a novel about books and technology, cryptography and conspiracy, friendship and love" -- much of which could also be said about Little Brother. You probably won't learn as much about Aldus Manutius, early printing, and font punches in that book, though.
books like little brother