My very favorite technical book of last year was Peter Seibel's Practical Common Lisp. APress has recently released Practical OCaml by Joshua Smith. OCaml is the language implemented by F# (I don't know if F# is super- or sub-set -- perhaps the book will clarify).

I doubt that lightning will strike twice, but if Smith's book is half as good as Seibel's I look forward to reading it.