Sending query like array with coma separated to URL and echo the selected checkbox
I am having a problem to send coma separated value to url which is like as below;
I have created a repeat region where all the books names shows in separate checkbox, after that i select some random book by selecting the checkbox and after submit the value for search it shows url like book=3&book=20&book=8 and for this only the result comes from one book only and not from all the books but if i can send the query like book=3,20,8 then I get the results from all the books.
Also I need to echo back the selected checkbox which I selected before passing the query so that I know which books I selected.
The example live page is
Please help. I am sending the login info in the PM