Shock ! Horror! Panic !
I've got loads of them of course. I got half way through the Penguin Russian Course, and it's a smashing book, brilliant .... and all that. I've read nearly all of Colloquial Welsh but only by dipping into it over several years. Ditto various Spanish, French, Russian (etc) course books.
You see, ploughing through these books from start to finish is just not the way I do things ... it's not my "learning style" as they say in certain circles. I'm a Butterfly-Minded Hopper-Around ... I'm sure there's a proper name for it, but being a BMHA is my thing.
I much prefer to just get on with reading stuff and listening to stuff and trying to speak about stuff, and I use the grammar books and course books to dip into and prop me up when I need propping up.
Alles Klar is one such prop ! By the way, it's not really that small ( see above). The thing is, it's funny, it's brilliantly written and set out, and it covers loads of grammar in an interesting and sensible way. The questions and exercises are also very useful and cleverly devised as well. Also, the Amazon reviewers love it too. Also, it's cheap .
There's other German books as well... oh yes ! But for now, let's have a spot of music ... it's Klee with Zwei Herzen ...