Exploring audio ebooks through Overdrive was a learning experience. First I had to install the Overdrive Media Console, then upgrade Windows Media Player before I could check out a title. Because Baltimore County Public Library offers Overdrive titles through their website as well as their catalog, I needed only a library card number to access the account. Some titles are listed as "always available." Others need to be put on hold.
One of the titles always available was "Jefferson's War" by Joseph Wheelan. It could be downloaded as a total volume, or in parts. Once I was able to download this book, it was great to hear Patrick Cullen reading the narration. I can see why people prefer audiobooks in this format. They can be accessed from home and do not have to be returned. After 21 days, they expire.
Project Gutenberg has a better selection of titles on Lincoln, including the biography by John Hay and John Nicolay. Gutenberg offers an option to download in Plucker format, which apparently can be sent to a cellphone. I chose to use the online reader. It was very convenient to be viewing the original text of this biography in a PDF-type file.
Project Gutenberg is free, but asks for donations to keep the project going. Their selection is worth it. They also offer the opportunity for readers to proofread some of their texts.
Both ebook libraries are excellent, with Gutenberg having the edge for more academic volumes. I would recommend Overdrive for popular reading, and Gutenberg for searching harder-to-find works.