Discussions of whether OCaml is "practical" or useful or good aside, this book really, <i>really</i> needed to be written.<p>It may be the case that there are truly excellent resources for learning OCaml, but I know the language, and I've never heard of them. There's Jason Hickey's tutorial, an introduction or two scattered around the internet, and some book that was fan-translated from French, sure, but OCaml lacks the hackerly dialogue that typifies discussion of languages like Haskell. It is a problem, for example, that these usually very incomplete hobbyist-curated tutorials almost always outstrip the professional literature: when people do publish books about OCaml, they are often littered with errors or flat-out wrong (I'm looking at you, Practical OCaml).<p>Regardless of whether we can all get on board with asynchronous whatever, or pronouncements about its "real" speed, or whether it should be used when Haskell is around, it is clear that there is a huge divide between the people who actually can argue these things well, and those who cannot, and switching from the first group to the second by yourself is tempestuous and trying. Is it the case that there are no OCaml experts in the world? If you are going by the amount of information on the Internet, it is not really obvious that this is actually the case. How can you, then, become one?<p>Besides that, though, having a sound OCaml counterpoint will do communities like Haskell good. I hope this finally ushers in the golden era of learning OCaml. Not everyone can take CS51 at Harvard, and besides, the credulity of a real (and good?) book about OCaml will hopefully advance the dialogue further than the typical questions of whether it can actually be done in X, Y and Z enterprise environments. That is a debate I (and probably many OCaml fans) have heard enough of.