Peterson First Guides are the first books the beginning naturalist needs. Condensed versions of the famous Peterson Field Guides, the First Guides focus on the animals, plants, and other natural things you are most likely to see. They make it fun to get into the field and easy to progress to the full-fledged Peterson Guides.
Pretty much all of these Peterson guides are first rate. Each species gets the treatment, including full-colour plate, ink drawings for distinguishing details, range maps, etc. Indispensable, if you're into this sort of thing.