In many autonomous regions, schoolbooks are free, recycled a couple of times by the schools. Others work with ´cheque libro´ that will enable you to purchase most schoolbooks at a local bookshop with usually just the odd workbook (that needs to be written in so cannot be re-used) to pay for by the parents themselves.
In Valencia apparently no such subsidy was in place, but the new ´Compromiso´ government has introduced it for this schoolyear. Families with children going to primary or secondary school can get a refund of 200 euros on the textbooks they have to purchase for the schoolyear 2015/2016.
The subsidy is divided in two parts. You can claim the first 100 euros, on showing the receipt for the books, at local Town Hall. The other half will be forthcoming for those that return the books in good condition to the school next June, at the end of the schoolyear.
These books will be included in a ´book bank´and those that returned the books in good condition, will be able to benefit from that and obtain the necessary textbooks for their children free of charge the next year.