An eBook, or "electronic book", is a publishing format by which a book is created, distributed and read as a computerized file, as opposed to being printed on paper and bound.
Most recent Star Trek books are released simultaneously as eBooks and in traditional print formats. An increasing number of older Trek titles by Pocket Books which are no longer in print as physical books are also available as eBooks. However, titles indentified as eBooks in this wiki are primarily works that are released exclusively in electronic format, such as the Star Trek: Starfleet Corps of Engineers series. These works are reprinted in physical omnibus books at a later date.
Until 2006 the only exclusively eBook released literature was the SCE series, however with the relaunching of the series to Star Trek: Corps of Engineers a reduction was made to the number of stories in the series to make room for other eBook projects. The first such events were two miniseries each celebrating the anniversaries of TOS and TNG; Mere Anarchy and Slings and Arrows.
At the conclusion of the Slings and Arrows miniseries in early 2008 Pocket Books have put the line of original eBooks on hiatus. 
Pocket revived the original eBook in 2011, with the release of The Struggle Within.