It's needed and should be valued as such.
This is a thoroughly un-inspiring read. conversely it is also a must read.
If you're doing level 2 electrical studies it will help you pass your 203 tests. You might well find the tables helpful for working out containment and cable sizing.
This is supposed to supplement the outrageously priced Regs' book. (again a must have) and indeed it will do that.
In this modern era of electrical safety and the speed in which updates 'should' be rolled out I'd much rather find that the regs' become law (but that won't happen because then they'd have to be open forum and free) and they are available for a yearly subscription fee online where I won't have to use glue to stick on pages that were misprinted.
Overall, I love this little book. I love that very clever people have done a lot of the graft of discovering the details and made it possible for us all to step on the shoulders of giants. (Tesla, Flemming, etc) Buy this, study hard, be safe with electrics and good luck.