Apparently I bought this at least 7 years ago, as I bought it along with The Prize (a doorstep about the history of the oil industry) and Lolita. These were all at the recommendation of a colleague, and I think it says something that I managed to get through the doorstep quite quickly, but took until now to finish this. I never got through Lolita.
Ignore the first half of the book, with run-of-the-mill logic/paradox puzzles. The second half is a fantastic introduction to combinatory logic, under the guise of puzzles about birds!
I'd stalled in a couple of previous attempts, when the trickier puzzles and subtleties unaddressed by the text started to pile up. This time around, I just wrote myself a solver to bypass the more tedious pencil-work, and pushed through the theoretical questions - which were often answered later in the book!
My workings are on github, along with some more in-depth thoughts on the book. The summary, though, is that this book is worth it if you're a fan of theoretical computer science, but not a hardcore expert.