My kids have been engrossed in this series for a while now. Both N (6) and M(2.5) love to pour over the detailed illustrations with their paper "flashlights" and they always find something new each time they look at one of these books. It's a little tricky to explain the concept behind this series and you won't really get it until you hold one in your hands but let me do my best. Each two page spread has one side with some explanatory text and things labeled to find. On the opposite side is a transparency on top of a jet black page. The child uses his paper "flashlight" (Taschenlampe) which is really just a piece of white cardboard to illuminate things on the transparency which don't show up when backed by the black paper. So the entire page is never in view all at once and the child can really explore the page and find the creatures lurking in the dark corners. It seems to hold their attention well since they must actively search out the subjects of the page.
It's low tech, got tons of detail, and works well for beginners who are just picking up vocabulary through profis who want technical details.
The transparent pages are sturdy and we've not lost a Taschenlampe yet, although if you do, it's easy to make one out of stiff paper. There's a slot at the back of the book to hold the Taschenlampe when not in use.
Licht an!, part of Meyers Kleine Kinderbibliothek from Alphabet Garten