diesel-ebooks.comは安全ですか？

Bought an eBook on their website. Their instructions for Nook at the time (7-16-2013*) did not work for my Nook HD+. Wrote their customer support asking for help. Their response: "As the NOOK HD is a newer, tablet device and it requires either the free Diesel app OR bluefire to download the ebooks off our site. The original NOOK reader can transfer from the PC to the device as the provided instructions state. I have on my 'to do' a note to write nook HD directions." So I am told that to view the book I am to install one of two poorly rated (3.2/5 & 3.4/5 stars) apps unknown to me and accept that their instructions were incorrect? Fine for some, but not for me. I emailed them back asking for a refund; they just "cut and pasted" their previous email again. A customer should not have to worry whether an online merchant's instructions are accurate and up to date. * http://support.diesel-ebooks.com/kb/article/hardwaredevice-questions/bn-nook/can-i-read-your-ebooks-on-the-barnes-noble-nook