Designing Data-Intensive Applications is available from your favorite bookstore.
Ebook ISBN: 9781491903100 (1491903104)
Beware: the Google Play store sells a PDF edition of the book, but it does not have the print layout or O’Reilly design! Google appears to have converted the ePub to PDF, and the result looks terrible. Don't buy it! eBooks.com sells the properly formatted PDF.
Print ISBN: 9781449373320 (1449373321)
Note: some of the links above are affiliate links that earn me (the author) a small commission if you buy through them.