Most of the classics are available for free from Google and Project Gutenberg.
Google's books are usually just scans that are not proofread and contain many OCR errors.
Project Gutenberg books are scans that are then proofread by volunteers and tend to contain far fewer errors.
For just a few dollars you can download books from the B&N classic series. These books have been professionally converted to eBook format by Barnes & Noble and in addition have added content with information about the author, the time period the book was written in, and footnotes explaining terminology that might not be obvious to a modern reader.
In my opinion the best choice is always the B&N classic, if it is available.
I think the OP means that when you do a search you get several variations of the same book on BN.
OP stay away from the Pubit ones.