Allen's and Greenough's New Latin Grammar for Schools and Colleges Founded on Comparative Grammar
The information is presented in the most concise way. It feels like everyone involved in creating this work loved the Latin language. It is bursting with helpful charts and examples. Everything is explained, from the Latin alphabet and the parts of speech, to roots and stems, all the way up to the intricacies of the myriad of rules for the different kinds of clauses.