+## Recommended Books ##
+
+It's not *mandatory* to purchase these for the class. But they are good ways to get a more thorough and solid understanding of some of the more basic conceptual tools we'll be using. We especially recommend the first three of them.
+
+* *An Introduction to Lambda Calculi for Computer Scientists*, by Chris
+Hankin, currently $18 paperback on
+[Amazon](http://www.amazon.com/dp/0954300653).
+
+* *The Little Schemer, Fourth Edition*, by Daniel P. Friedman and Matthias
+Felleisen, currently $29 paperback on [Amazon](http://www.amazon.com/exec/obidos/ASIN/0262560992).
+This is a classic text introducing the gentle art of programming, using the
+functional programming language Scheme. Many people love this book, but it has
+an unusual dialog format that is not to everybody's taste. **Of particular
+interest for this course** is the explanation of the Y combinator, available as
+a free sample chapter [at the MIT Press web page for the
+book](http://www.ccs.neu.edu/home/matthias/BTLS/).
+
+* *The Seasoned Schemer*, also by Daniel P. Friedman and Matthias Felleisen, currently $29 paperback
+on [Amazon](http://www.amazon.com/Seasoned-Schemer-Daniel-P-Friedman/dp/026256100X). This is a sequel to The Little Schemer, and it focuses on mutation and continuations in Scheme. We will be covering those topics in the second half of the course.
+
+* *The Little MLer*, by Matthias Felleisen and Daniel P. Friedman, currently $31 paperback / $29 kindle
+on [Amazon](http://www.amazon.com/Little-MLer-Matthias-Felleisen/dp/026256114X).
+This covers much of the same introductory ground as The Little Schemer, but
+this time in a dialect of ML. It doesn't use OCaml, the dialect we'll be working with, but instead another dialect of ML called SML. The syntactic differences between these languages is slight.
+([Here's a translation manual between them](http://www.mpi-sws.org/~rossberg/sml-vs-ocaml.html).)
+Still, that does add an extra layer of interpretation, and you might as well
+just use The Little Schemer instead. Those of you who are already more
+comfortable with OCaml (or with Haskell) than with Scheme might consider
+working through this book instead of The Little Schemer. For the rest of you,
+or those of you who *want* practice with Scheme, go with The Little Schemer.
+
+* Another good book covering the same ground as the Hankin book, but
+more thoroughly, and in a more mathematical style, is *Lambda-Calculus and Combinators:
+an Introduction*, by J. Roger Hindley and Jonathan P. Seldin, currently $74 hardback / $65 kindle on [Amazon](http://www.amazon.com/dp/0521898854).
+This book is substantial; and although it doesn't presuppose any specific
+mathematical background knowledge, it will be a good choice only if you're
+already comfortable reading advanced math textbooks.
+If you choose to read both the Hankin book and this book, you'll notice the authors made some different
+terminological/notational choices. At first, this makes comprehension slightly slower,
+but in the long run it's helpful because it makes the arbitrariness of those choices more salient.
+
+* Another good book, covering some of the same ground as the Hankin, and the Hindley & Seldin, but delving deeper into typed lambda calculi, is *Types and Programming Languages*, by Benjamin Pierce, currently $77 hardback / $68 kindle on [Amazon](http://www.amazon.com/dp/0262162091). This book has many examples in OCaml.