For those who haven't been able to pick up the paperback Kingdom Hearts publications that have been released in the past couple years, Yen Press has now conveniently begun releasing their English publications electronically via e-books. On March 21, 2017, Yen Press released Kingdom Hearts: The Novel electronically for $7.99 USD.
Furthermore, on April 18th, Yen Press will be releasing Kingdom Hearts Chain of Memories: The Novel electronically for $7.99 USD.
With these electronic releases, Yen Press will also be releasing the newest publications Kingdom Hearts II Vol. 4 ($6,99 USD electronically) on May 23rd & Kingdom Hearts II: The Novel Vol. 1 ($7.99 USD electronically) on June 20th, both available for the first time in English and for purchase electronically on day 1.
You can click on book titles to check the book page and find out where to buy each e-book.