problem about books

I have a mac mini.. My problem is that i bought some books fro the itunes, and i cant read it..!! I press the button to open the book, and it tells me that i must downoload tha''ibook''..!! but when i went to download it, the ibook is only for iphones and ipod and ipads.!! I have mac mini!!! and i cant read my books , whick i bought..