Conjugation is where enthusiasm for Spanish usually runs into trouble. Vocabulary can be picked up almost incidentally, whereas verb endings have to be drilled until they arrive without thought. Juan Pablo Cardona builds a course around precisely that problem, and the subtitle, Basic to Intermediate Workbook, states the method plainly.
Forty-one hours is an extraordinary length for a language recording, and it makes sense only as repetition. This is not a book about Spanish grammar; it is grammar practised aloud, over and over, in the format that actually builds fluency. Our catalogue files it under education and learning, and it belongs there more literally than most titles on that shelf.