A newbie Calibre user seeks advice.

[gaving]

Hi all - I have a couple of questions regarding Calibre that I hope you have the answers for - please try not to be too technical if you reply as I am new to this!

I have Samsung A7 10.4 inch tablet. Firstly, I downloaded a book to the Calibre library in PDF format (Mobi and Epub mess up the book contents). When I sent the book to my Kindle app on the tablet it shows on the Kindle home page and the KIndle library page a generic PDF cover in grey and red which I do not like. Upon clicking on the PDF cover, the cover changes to display the correct picture. I would like the correct picture displayed on the home and library pages as well if possible.

Also - can you recommend the correct book cover size for my tablet, because when the book cover displays, it leaves 2 black borders, one on top, one on bottom. I have tried resizing it using online photo editing, and Calibre's own Resize Cover plugin but just can't seem to get the correct width and height.

Many thanks,

Gavin.