I have just finished reading my first full-length book in German, a bundled pair of short crime novels (around 130 pages each) by Friedrich Dürrenmatt: Der Richter und sein Henker and Der Verdacht. I had read Brecht's Leben des Galilei some twenty years ago and last term I read Biedermann und die Brandstifter for a reading course at the Language Centre, but those are much shorter plays.
Reading the Dürrenmatt novels involved sitting in front of a computer with an online German dictionary open, but progress was still rapid enough that it felt like I was reading a book, not doing a language exercise. As well as having relatively simple language, it helped that the novels (originally serialised) are fast-paced and varied, with relatively short, contained chapters. Next up I'm reading Irmgard Keun's Das kunstseidene Mädchen, again with an online dictionary to hand, but I'm also going to try Erich Kästner's Emil und die Detektive - Helen can't have all the children's books! - without. It may be some time before I'm up to reading the (as yet) untranslated volumes of Die Ästhetik des Widerstands, but that no longer seems like a completely unattainable goal. My spoken German is still woefully weaker than my reading, but next term I've signed up for a speaking course which might improve that.
It's been a long haul from when I did German in year 10, when the teaching seemed rather vacuous (compared to Latin) and I spent the classes reading Kafka (in English) under the table, through an introductory course at uni and an assortment of textbooks and readers.
It's interesting comparing my second language acquisition with Helen's first language acquisition. I'm quite possibly learning new vocabulary almost as fast as she is, but not nearly as effectively and clearly in an entirely different way, as she's often learning the ideas alongside the words. It's no longer the words I don't know at all, typically slightly more obscure, that are the biggest problem — they can usually be guessed at from the context — but the less common meanings and uses of common words. This also changes dictionary use: compare the complexity of entries in an English dictionary for "put" and "paraphyletic".