If you ever want to watch an amateur classicist go up in flames and start channelling Cicero at his most denunciatory and his least fair-minded, start up a conversation about the quality of Greek and Latin textbooks. A very few books may get positive comment, but for the most part these books aren't friendly to the autodidact. It's one reason why Textkit's forum is always going to be popular. While there are books I warn people away from, for the most part I don't usually get too agitated about textbooks. For the self-teacher, it is far more important to stick with one than it is to succumb to the temptation to churn through a dozen books hoping to find one that makes the middle perfect of consonant stem verbs easy to learn.
That said, I'm going to complain about Greek textbooks now. Well, make a slightly cranky observation.
When I was in high school, by the time I got to the second year of French and German, the textbooks we used were introducing some grammatical material in the language being taught, along with obvious things like calling chapters chapitres and describing the requirements of homework auf Deutsch. Even the mechanics of day-to-day classroom work were turned into another opportunity to use the languages which, in theory, the classes were supposed to impart. I have seen a few Latin textbooks which do use Latin for more than just the exercises. The only book I've run across doing this in Greek was published in Spain in 1856 (Google Books), and that's clearly an advanced book.
So, it seems to me that by the time you start learning about -μι verbs you should be seeing Greek not only in the terrifying new construction the lesson presents, in the idiotic practice sentences and in whatever adapted passage of literature that lesson has, but also as the chapter headings, in the notes explaining tricky parts of that adapted passage, etc. On the other hand, I've recently been working on a page for Scholiastae.org which describes ancient Greek grammatical vocabulary, Greek Grammar in Greek, intended for people who don't want to drop to English in the Greek- and Latin-only sub-forum. There's a lot of Greek grammatical vocabulary. The beginner to Greek already has to learn to cope with strange incantations like "aorist middle optative" in their native language. Are the benefits of seeing more Greek worth the cost of learning the substantial technical vocabulary when lots of more basic vocabulary also needs to be learned? Since no one is forced to learn Greek any more, I'm inclined to see value in laying on Greek as thickly as possible for those few who do decide to take it up.