Square Enix announced that the NieR: Automata World Guide is available to purchase digitally in Japan. It will cost 1,870 yen, or roughly $16, and is immediately available to download for the Amazon Kindle. The digital version of the NieR: Automata World Guide will not feature a text-to-speech option. Additionally, the disclaimer on the store pages mentions that certain information in the book may differ from when it was originally released in February 2017. [Thanks, Famitsu!]
Additionally, the NieR: Automata Strategy Guide is available to purchase digitally. It will cost 2,586 yen, or $22. It will feature the same content as the original release of the physical edition in April 2017.
The NieR: Automata World Guide features 192 pages of artwork and development details. Additionally, it features a total of two novellas written by Emi Nagashima. Her previous work includes the Drakengard 3 short stories, and the manga adaptation of Drakengard. However, the digital version of the World Guide is currently only available in Japanese. As of writing, there is no indication that the World Guide or the Strategy Guide will be available to purchase digitally outside of Japan.
NieR: Automata is immediately available for PlayStation 4, PC, and Xbox One. It first released for the PlayStation 4 in Japan in February 2017. A Western release and PC release followed in March 2017. It released for the Xbox One in June 2018.