Standard Ebooks,
Project Gutenberg and our own
MobileRead Library are all excellent sources for classic public domain books. Most have been converted very well indeed.
If you really want to buy instead of getting free, I've bought from
Delphi Classics in the past, and I was pleased with their product.
Buying any public domain book on Amazon is generally a bad idea. There are enormous numbers of editions, mostly from 'publishers' who have just repackaged whatever public domain copy of the text they could get their hands on - mostly the Project Gutenberg one.
For Trollope (as least his Chronicles of Barsetshire), I recommend the omnibus in the MobileRead library by HarryT, who carefully corrected all errors he could find in the public domain texts.
https://www.mobileread.com/forums/sh...ad.php?t=53279