I try and read/comment on all of the OCaml articles that surface here. I've been learning the language for a few months now and I'm having a blast! I'm hoping we can carve out a niche in the infrastructure space for OCaml. It's a really approachable language for the ML family! I hope it grows.
Here's a couple of books I'm enjoying so far:
Think OCaml/How To Thinke Like A (Functional) Programmer - http://greenteapress.com/thinkocaml/thinkocaml.pdf (same author as all the other awesome Think X books!)
Unix Systems Programming in OCaml - http://ocaml.github.io/ocamlunix/
People also say really great things about Real World OCaml but I haven't had a chance to go through it yet.