The first Gen Kindle Fire has a common problem with the charging port, if you read it and move it around while charging, the solder can break, making it so the unit won't charge. (some discussion
here, how to repair if you know how to solder
here.
When a new one starts at ~$85 , I can't see bothering with a used Fire of any generation.
The Fire series are essentially tablets, with lots of Apps available, and if you are a member of Amazon Prime, are pretty good for watching streaming videos.
You can load books that you buy from Amazon automatically (if you buy from them it will be automatically registered to your account), or you can just copy files in the
correct format to the Kindle from your computer. There are a lot of books that are public domain.