There might be a better 'introduction to syntax'-type book out there, but if there is, I haven't read it.
In combination with "A Dictionary of Grammatical Terms in Linguistics" (Trask, 1996) (which I also think is great), this book is excellent for the following reasons (in no particular order):
1: It neatly breaks down syntactic analysis into two views (dependency vs., constituency), but not without forewarning (and later explaining how) they aren't exactly so easily separable.
2: It offers simple methods for defining all the different 'types of words' you could come across, like lexical categories, constituent phrases and grammatical relations. Lots of introductory syntax books do this, but here Van Valin makes it concise, easy to follow, and (almost) self-contained (it is a bit hazy in parts - for example, I'm still not really sure what syntagmatic vs., paradigmatic relation(ship)s are)?
3: It ends you up in a position (at least feeling) ready to take on tougher texts. The pages are all pretty dense, and the final chapter seems to offer really good mini-introductions to various theories and ideas, which are all either currently relevant or have been important in the build-up to the present state of research.