Is this a book with a free CD, or a CD with a really big inlay booklet?
Geoff Sample provides about 70 minutes of detailed British birdsong recordings, enhanced by equally detailed written notes. Although much information is duplicated in both (handy for revision), the prose differs in each. On the one hand the book contains more facts than the CD's narration, but on the other… well, there is simply no substitute for actually hearing the noisy critters.
I've just tried listening to the whole CD while reading the entire 30-page book at the same time, and while they do complement each other admirably, my brain's attempts to concentrate on both written words and audio at the same time were literally sending me to sleep. (clearly I'm no bird-brain)
This combination doubtless works best if you're trying to learn this stuff. Then you can dip into each in isolation as and when necessary. By the end of this I gave in and just lay back with my eyes closed taking in the beautiful melody.
And I have to hand it to the recordists. Convincing the natural world to perform in front of a microphone must be both time-consuming and highly frustrating, yet thanks to these guys I can enjoy these spectacular charms of nature in comfort. The pheasant on track 94 sounds human!
Next time I go out to the garden, I'd better pay a bit more attention.