CDs are always better than books to study from as you can hear the right pronunciation.
If you see new words in a book, it can be difficult to know how to say them.
However some books use katakana symbols to show the reading. Katakana is Japanese, not English.
If you see a word in katakana, It's not English but Japanese Gairaigo.
The problem is not R or L, the problem is that there are too many syllables in katakana.
It gets too confusing to understand. No-one will understand you if you learn English through katakana. Well, actually if the other person speaks Japanese they will understand. But if they speak Japanese, you don't need English, do you!
You want to be able to speak English to people who don't speak Japanese, right?
Some people say that katakana is close to English, so It's OK to use it.
They say It's a “starting point”, something to help you.
I say that it is simply wrong.
They say “but It's close to correct English”. But That's still no good. Katakana is the same, It's close to English, but It's wrong.
So don't use katakana, use CD or movies. Practice every day and you'll have no problems.