Recently, I was looking for a textbook to refresh my knowledge and I stumbled across First Latin lessons by Harry Fletcher Scott. It is by far the best Latin book that I have ever seen. It reminds me of a cross between Wheelock and Lingua Latina because it gives very detailed grammatical explanations, but is based around reading passages. It also explains what the grammatical concepts, eg. an intransitive verb, mean, which I find really helpful. The book proceeds very slowly and explains everything at length. For me it has everything that perfect Latin book should have. First Latin Lesson covers about Chapters 1-27 in Wheelock, except for the dative of agent and the passive periphrastic. A junior Latin reader continues where First Latin lessons leaves off and finished the grammar. I strongly recommend this book for anybody who wants to learn Latin and have no idea why this book is not more widely known.
FYI: I looked at the 1930s revisions of this textbook and they are worse than the ones at the IA.