Books won't sync to my iPhone.

I recently downloaded a couple of books on my laptop (windows 8) and put them onto my itunes. When syncing them to my Iphone 5c (9.1), it said in the bar at the top of itunes that they were being transferred to my phone, but when I opened ibooks on my phone the books were not there. I tried multiple syncs but the books would not transfer to my phone. I decided to take all the books off my phone (unticked the box in the books tab when the phone is connected) and put them back on. Only now the majority of my books were not transferred to my phone, they were all on before. The only books that were transferred onto my phone were books that were downloaded directly from my phone, not from my laptop. The books are a mixture of EPUBs and PDFs. I have tried syncing all my books in one go and have tried individually putting single books onto my phone, but none would transfer apart from the aforementioned. I have searched the internet for a solution and have tried a few that people have suggested but none have worked. Is there anyone out there who has experienced this problem and can help me out??