.mobi files

I was searching for something in my downloads folder and found some .mobi files from 2008. I can't open them, and since I have no idea what they are, they probably aren't important. I did a search on .mobi files, and from that my best guess is that they may be chapters of an eBook. They have apparently been moved from computer to computer whenever data was transferred to a newly purchased device. All but one of them are the same size (2.2 MB) and were downloaded on the same date. I'm inclined to move them to the trash, but maybe it would be best to find out what they are. Without going to a lot of effort for something I apparently haven't thought about in more than a decade, how could I open them?