Regarding unfinished books, since Leanpub is a self-publishing platform, we don't typically have any knowledge of an author's life circumstances, or their writing project plans. Sometimes book projects can get stalled for a long period of time, and the author will come back to them.
There are a lot of reasons an author might stop working on a book for a while, including developments in their personal and professional lives. So, sometimes a book project might get stalled for a while.
To find out what the author's intentions are for book, we recommend you contact the author and ask them directly about their plans.
Here are the instructions for contacting a Leanpub author: