Recently I was looking around Amazon to see what their best-selling books were for learning Spanish. I navigated the reference books section to the category Words & Language, and then to Linguistics.
Looking down the list for books in Spanish, the first two books I found were really cheap and could be useful. The first one got a lot of five-star reviews from readers, the second one a bit less.
[1] I remember this Dover book from when I was a librarian. At two dollars, a bargain… and a lot of vendors are selling copies for one penny (but they usually make up for it with higher shipping).
I made the image large so you could read the contents. As usual, clicking on the image takes you to Amazon
[2] Here’s another vocabulary-builder, for the same price and also from Dover:
Being a former librarian, I did my obsessive bit to see if possibly these two books were different editions of the same thing but they do not seem to be.

