Actually, if you understand what Logos truly does, its a gem. It gives you the ability to add docx files as "Personal Books." Scan your book, turn it into a docx file, upload it. Do it for all your books. Then, you sit at your computer and say, "search for John 3:16", or any search, and in less than a second, all the hits come back. You can search your entire library in less than a second.
Done right, its like having Star Trek's computer at your fingertips.
Logos is free, empty. Just download the free version, create a free account, add your docx books, and its awesome.
I have my whole library in my computer in Logos, and backed up. All my reformed and puritan works except a few volumes left.
Amazing tool.
However, there's not a chance Im paying Logos for all those electronic versions. I just created them all myself. Takes some time, about 4 months. But totally worth it.