If you want syncing of books highlights and notes on an Android, them you might want to looks at Mantano.
There are three different versions available in the Play store, ranging from free for the basic one up to around £7 or so for the premium version. They also have a cloud service available for syncing, although there is a small yearly charge to use that.
Mantano is also one of the better epub readers out there and it also supports pdf as well.
And it's got an excellent library management system which will also sync.