The Taxi series is an ongoing series that revolves around a lesbian couple in Berlin in the early 90s; their everyday struggles with each other as well as with friends and family.
If you want erotica, this series is NOT for you.
If you like character driven soap operas that focus more on the relationship rather than on sex, and that touch many different issues while not lacking a humorous side, this series might be for you.
You can find free PDFs of the first ten books in the links below. Enjoy