I agree with @Jayadev wholeheartedly, i.e. the courses and exams are geared toward real world applications, so to that end, if the course is worth taking (from your perspective), the book is probably good to have...
That said if you are wondering about some good courses and therefore good books I'd suggest RH342.
I still refer back to the PDF for troubleshooting filesystem and LVM issues that I don't encounter regularly.
You will notice that ROLE courses feature a HTML book, rather than a PDF one, and as such, can not count against your download limit.
I'd be interested to hear what courses in ROLE have the PDF download option.
At any rate, the limit is for any sort of PDF download, regardless of modality, as long as the download is enabled by your RHLS, and not some other entitlement (such as attending Virtual Training purchased separately).
I think any ROLE has or at least the most famous.
check the picture there is a button on the right where you may doawnload a PDF, plus VC also will be same ROLE PDF cause inside it is written ROLE, but ROLE I saw it's newer version of courses.