By David Brin.
This sci-fi book is based on a cute premise, but I found the ending extremely unsatisfying due to its weak resolution. The premise is this: humans have colonised other planets. One such isolated colony chose, close to ten thousand years ago (if I'm interpreting the years given correctly), to modify humanity so that women reproduced clonally during the winter. However, men were still required to spark the process.
Problems with this book? Maia gets knocked on the head and kidnapped a lot of times. You get tired of it after a while. Also, she finds out partway through that she and her twin sister (genetic "vars" or variants, conceived during the summer) were named after characters in an old book who... let me guess... had the same idea to pass themselves off as clones that Maia and Leie had. Why? Respect for someone who managed to establish a clan of clones is automatically higher than for genetic vars, who are cast away by most clans when they reach their fifteenth year.
Some of the plot twists (Renna's identity) are a little too obvious, while too many other questions go unanswered. And the ending is quite weak, while not appearing to have a sequel. Not a great book, but not unreadable. However: other opinions may differ. Apparently it was nominated for a Hugo award in 1994.