Barnes and Noble has all four books on one easy-to-access page.  Click on the link below, and you'll be taken to that page!

http://www.barnesandnoble.com/s/Mark-W--Danielson?keyword=Mark+W.+Danielson&store=allproducts

Diablo's Shadow available at Diesel ebooks.

http://www.diesel-ebooks.com/item/9780979916755/Danielson-Mark-W.-Diablo-s-Shadow/1.html

Orders for Bookstores and Libraries

Bookstores and Libraries can order Diablo's Shadow (Night Shadows Press) from Ingram Book Company

Diablo's Shadow will be carried at local booksellers:

Tattered Cover 

LoDo, Colfax and Highlands Ranch locations