A useful application to read and explore the Arena chess opening books (ABK).

The study of chess openings is very important regardless of the strength of a player. Everything you know about middlegame or endgame will be useless if you get a bad position in the opening. To be successful in chess, you need to have a strong knowledge of multiple opening variations. Having studied the opening, you will often come across familiar positions in which you know what to do, and having got the advantage in the opening, you will feel more comfortable in the middlegame and in the endgame. In addition, knowing the openings will help you save precious time during the game.