My advice is similar to what was posted here already lol but it has been pointed out that I am the beginner's forum PLO poster.
I haven't read a single PLO book lol so that tells you that you don't have to read a book to learn.
You need to read the posts on the Omaha Hi forum. Start playing at the lowest stakes for practice and post as many of your hands as possible on the omaha Hi forum so you can get input.
General PLO rules to keep in mind
#1 Starting hand selection: Not as key as it is in holdem but starting hands are extremely important in how your hand will play out to showdown. Hands that play out extremely well are consecutive cards such as 9JTQ and even better and more importantly double suited. You want to avoid playing hands like A6T9 single suited. This type of hand doesn't play out well. The hands which most often win in PLO are trips, straights, flushes, and boats. Consider how likely it is to get that type of hand when you select your starting hand. Use this point system at least at first to get the idea of what hands are GOOD:
http://erh.homestead.com/omaha.html
#2. Postion is very important in PLO. You get to see what the other players bet first and you get to control the size of the pot. You can see weakness or strength. Easy to tell if they bet they are strong if they don't most likely they are weak.
Try to avoid rasing in early positions even with good starting hands. Especially with AAxx this is a death sentence because everyone knows you have aces and will destroy you. Had it happen many times to me.
#3. Aces, although profitable in PLO, are not the be all and end all. It is good if you can isolate the betting between you and one other player but it plays poorly multiway. So if you are in late psotion raise as high as you can to isolate your opponets. Aslo understand that DRY aces are not worthy of rasing ( dry aces are no suited aces in you hand)... the best is double suited aces or aces with connectors like AAJT dbl suited... love it push it in late psotion.
#4. Two pair is always over played by Holdem players who come to PLO. Don't be the lead better in a pot with just two pair because two pair rarely wins in this game. There is more to this but just keep it in mind.
#5. Holdem players are used to bluffing... if you are new to PLO DO NOT BLUFF.... it won't work! You will go broke if you try it and don't know how to do it. Bluffing is an advanced move that I am still experimenting with myself. You should avoid it until you fully understand the game.
There is so much that can be covered... but I am tried lol so this is all I am writing for now... Good Luck.