You can find out many nice pool themed games at App Store. But if you want to compete with your friends, the following pool game 8 Ball Pool may be more suitable for you.
8 Ball Pool is a multiplayer based pool game developed by Miniclip, and designed for both iPhone and iPad. The iOS game features gorgeous vibrant game graphics, realistic sound and physical effects, and simple touch controls. Of course, same as most pool games, all you need to do in the game is to hit the eight balls into pockets faster than your opponent, however, this time your opponent isn’t computer but your friends. The multiplayer game mode allows you to compete with your friends on the same pool table, apart from that, random mode lets you compete with other players around the world, and earning pool coins that help you enter higher ranked matches.
8 Ball Pool with a size of 38.4 MB is compatible with iPhone (optimized for iPhone 5), iPod touch and iPad running iOS 4.3 or later. The iOS game is priced at $0.99 USD, but in view of its pool coin system you can also wait for its free availability. If you’re interested, jump to App Store for more details.