Just as a note guys -when using Calibre simply right click on the title you wish to send to your android device and scroll down to send to device then on the sidebar that pops out send specific format- click that and choose mobi and that will send the file (book you chose) to your BOOK folder on your Android, all that remains to be done now is drag the file from the book folder to the kindle folder and Bob's your Uncle and Fanny's your Aunt!
PS If your book isn't in Mobi format you can simply convert it within the Calibre app before doing the above
