This is probably the best, most complete and most up-to-date reference grammar of Biblical Hebrew (BH). Jouon's original work was written quite a while ago in French and was translated into English, revised and expanded by Muraoka. Hence the English edition is referred to as Jouon-Muraoka (JM).
It covers all aspects of BH, spelling/orthography, phonetics, morphology/grammar and syntax. There are certainly other grammars and syntax guides such as Gesenius' (GKC) grammar or Waltke O'Connor's (WO) syntax guide, both of which are very good, but JM put all of these together in one body of work. It's well done and well worth the money. At the same time it's not to say that there one should not go beyond it and get GKC or WO as well at some point. To a person looking for one reference grammar, I'd highly recommend to get this first.
As I've reviewed a number of tools for BH and read a number of reviews by others, I must add one more note. This is a REFERENCE GRAMMAR, not a textbook. All too often people confuse these two. They are not the same and they have different functions. What happens all too often is that folks who are looking for a beginning/introductory textbook see a highly rated reference grammar and get it with the expectation that it's the best tool for them to learn BH. The opposite scenario is often true as well. How disappointed they are when they get it and after reviewing it find out that it's not what they were looking for.
Reference grammars are collections of grammatical principles, arranged by topic, in various degrees of completeness. Textbooks are typically intended for classroom instruction and are organized around lessons, most often formatted for 1st year/two semesters of college instruction) with vocabulary, section on grammar and exercises or reading passages to practice what was learned in each lesson. They typically have appendices with summaries of grammatical principles, verb tables, etc. but are seldom exhaustive and typically cover only what was introduced in the lessons themselves.