Listed below are the reasons why I prefer to purchase my O'Reilly books direct from them rather than go to other retailers such as Amazon.
For some titles, not all, you can get them in many different formats:
So however you want to read the books there will be a format you can use, mainly I am only interested to two formats, ePub and PDF. I have all the epub versions of the books on my iPad, I also have the pdf version of the book stored in my dropbox folder, so I can have access to my library from my Windows PC at work, or where ever I need them.
If you purchase an e-book and there are changes/updates to the book, O'Reilly email you, informing you there is a new version of the book and say that you can re-download the purchased book, free of charge. Note: Not all print books are available in ebook format.
With regards to e-books you have already purchased, you can if you require purchase the printed book and receive 40% off once the printed version. Personally I am trying to replace most of my books to e-books to save some space in my office at home.
This can be expensive which leads to another bonus. If you register your print books with them online you can then upgrade your printed book to the ebook version for $4.99. Just register the ISBN numbers on your account, then you can view a complete list of books you've registered and click the Ebook Upgrade button.
They have many offers on the site, they always have the buy two get one free deal, which could be handy if you know you need to purchase many books. They also have the "Deal of the day" where the books are 50% off, you can subscribe to this feed here.
I have had to contact customer support, as recently I purchased a book, which I had bought previously. The support on this occasion could not be faulted, they got back to me quickly and offered a straight refund without any fuss, no sooner had they taken the money from my card the money was refunded the next day.
As always I am always interested in your thoughts so if you have any comments or feedback then please feel free to add any comments, or you can mail me here.