I'm still using LR4.4, but the learning process would be similar. I purchased "The Adobe Photoshop Lightroom 4 Book for Digital Photographers" by Scott Kelby and read the first three or four chapters before digging into the program. there are some key decisions you need to make concerning location of files and some set-up parameters that are best done before you do much with the program.
I only have experience with Kelby Training LR books and videos and i recommend those highly. Kelby has a number of LR5 training materials available. If you don't want to spend any money on training materials, Adobe offers some very god free videos and YouTube has lots of free options.
I think you will love LightRoom once you get comfortable with it - I do.