Format. You may have a favored format of the books you read, or may change according to whether you intend to enjoy the book at home or while travelling. Many books are now available as paperbacks, hardbacks and e-books. Check whether your desired format is one of the options for the book.
Length. Books come in all different lengths, from shorts to novellas to novels. Consider whether you want a quick read or an extended story that you can really get your teeth into. As part of this process, check whether the book is split up into chapters, which will help you gauge how long each chapter will take to read.
Blurb. The blurb is the summary of the book that can often be found on the back cover of the book. Rather than simply reading the title (literally judging a book by its cover!) make sure you also read the blurb to determine whether this piques your interest and demonstrates that it might be a book that you will enjoy.
Explicit Content. Some books may be considered erotica though they are labelled romance, so check whether it has a rating or notes details of the content in the first few pages to make it less likely for offence to be caused. The details in respect of the type of story can also provide other information, such as whether there is a happy ending. Check these to ensure that it matches what you want from a story.
Series. Check whether the book is one of a series, which may mean that you will have to make further purchases in order to keep up with the story. If you are not prepared to commit in this manner, ensure that the book is a single title. Alternatively, if you want to purchase an entire series, check that all of the editions are still in print before buying the first title. Similarly, if the story comes in several volumes, you may be inclined to buy all of them from the outset so you can be ready to move onto the next volume once you finish one. Alternatively, it is prudent to simply check that the other volumes are in stock from your preferred retailer.
Author. The author of the book may have written other books so consider whether you might have enjoyed other examples of their books, which will make it more likely that you will enjoy the story.
Anthology. An anthology is a collection of stories, often by different authors. This will give you the opportunity to read lots of different styles, which will create the opportunity to determine which style of writing you like.