Does anyone know a webshop where I can by Battlefleet Koronus? Preferably hardback but pdf is also ok.
Battlefleet Koronus
You can't buy the pdfs currently due to rights issues.
There are other ways of acquiring them.
As for hardback you're going to have to use Amazon, Ebay, Half Price Book, sites like that to find a secondhand copy. Since it's not in print anymore.