Email From A Vampire, Sophia, Boy, S.U.N.D.S, The Sound Of Crying and Digital Romance Disorder can be purchased in paperback and for Kindle.
The paperback or kindle version of these books can be purchased on Amazon - simply click on the relevent link on the right.
Waterstone's and WHSmith and most good booksellers (in the UK) also sell the paperback of all these books in store, or they can order a copy for you if they do not have it in stock at your local branch. Simply give them the ISBN number, or title and author name.
Click above links to purchase