Please read this.
Textbooks all have one mother. Two million years ago some hairy ape-man or man-ape depending on which anthropologist you talk to, wrote the first one. It was written on clay tablets and weighed about 2500 tons. Since then all authors have read that book and created their own condensed version of it. Essentially, they read a very big ( and heavy ) book and wrote a smaller and lighter one. Since that mother of all math textbooks was an utter bore the children can be not be much different.
I like Martin Gardner books.