Confused about ADD information

I rather recently realised that my husband has ADD. I immediately started reading up on the condition. I also told my husband about my concerns and after so reflection we are now both convinced he has ADD. The sheer acknowledging of it has helped tremendously and I can feel that we are every day making progress in the right direction. I say we because I have realised that it means I have to change my approach as well. In our quest for more information I am confused over the different types of information there is. In some places only three ADHD types are mentioned and in some six types. They all have different symptoms and features that are more or less predominant. As recently as today I read about ADD in combination with OCD. I already suspected that my husbands compulsive behaviour would be related to ADD but I thought it was rather a coping mechanism than an expression of the ADD. Now however I cannot find consistent literature about how these two correlates. In fact research seem very inconclusive about ADHD or ADD, which is causing a lot of confusion for people, like us, trying to understand what it is we are dealing with. If anyone has any good advice or litterature recommendations beyond what has already been mentioned here, we would be happy to hear about them.