Yes, just pgn files. I use it to read my Everyman Chess pgn downloads, and also a free monthly pgn download of the games ( Mostly annotated), from Chess Magazine at www.chess.co.uk.
Forward Chess - Chess Studio - Chess Viewer - e+Chess Books - Chess King - Chessable
Anybody mention Chess PGN Master? To view / replay pgn games. One feature I like with it, is that you can switch to "Play against engine" at any position, and then you can go back to the main line of the game later .
I use Chess PGN Master and I think it's the best software on Android for viewing PGNs, play and analysis. I use it in combination with ebook software (Forward Chess, Chess King and Gambit Chess Studio) on my Android tablet when I want to go more in depth or play against an engine for a specific book position.

Was anybody able to install the e+Chess Books iPad app?
I have tried it but the app isn't available in Belgium. But I'm not sure if this is the problem, because I know from someone who lives in Dubai that he also wasn't able to install the app.
I think the app might be outdated
I'm interested in this app because it is the only interactive chess platform that has the endgame book "Silman's Complete Endgame Course"
http://eplusbooks.com/books/14-silman-s-complete-endgame-course-jeremy-silman

Was anybody able to install the e+Chess Books iPad app?
I have tried it but the app isn't available in Belgium. But I'm not sure if this is the problem, because I know from someone who lives in Dubai that he also wasn't able to install the app.
I think the app might be outdated
I tried to contact the support from e+Chess Books by mail but I didn't get an answer.
I'm interested in this app because it is the only interactive chess platform that has the endgame book "Silman's Complete Endgame Course"
http://eplusbooks.com/books/14-silman-s-complete-endgame-course-jeremy-silman

I think it’s out of date for operating systems and unsupported.
Forward Chess app stated that they reached out to Mr. Silman to get his endgame book on their app but they have received no response.

Is it limited to opening PGN files only? We’ve been considering all the apps and services that open electronic versions of published chess books for reading and play through the games or positions used in the book as chosen by the authors.