The Humble Book Bundle: Functional Programming by O'Reilly just launched.
Tier 1 books (pay atleast 1$ to get these)
- Living Clojure
- Learning Scala
- Becoming Functional
- Introducing Elixir
- Introducing Erlang
Tier 2 books (pay atleast 8$ to get these)
- Clojure Cookbook
- Testing in Scala
- Scala Cookbook
- Real World Haskell
- Functional JavaScript
Tier 3 books (pay atleast 15$ to get these)
- Clojure Programming
- Programming Scala
- Functional Thinking
- Parallel and Concurrent Programming in Haskell
- Programming Rust