Where can I get a music theory book for bass that has very easy examples recorded on cd, which comes with notation/music score together????

I bought Rock School Grade 1 and the examples on CD are too fast/hard - to keep up when you are sight reading, it felt more like grade 4/5, I need something easier slower?

Or am I just rubbish at bass :'-(
hal leonard complete bass method.
it's 3 books in one and comes with 3 cds.
if youre buying online make sure you get the version that comes with cds bcz there is a cheaper edition of the book without them.