It is precisly what it says on the cover : "Cut this book into 160 pieces, glue them together and you have your own paper clock that actually works".
I bought this little book some 18 years ago, and three-quarter completed the clock. I recently rediscovered it in my attic, but need to buy a fresh copy to complete it. (18 years in an attic is not good for a paper construction - my own fault)
The parts I did assemble did work, but you have to be very neat. Not suited for children under 15 (give or take a year). I heartily recomend to take a photocopy before, in case you make a mistake, so you can get make spare parts.