Burke’s Peerage is a book that lists the hereditary titled nobility of the British Realm (the Peers of the Realm, hence the title of the book). It contains biographical facts such as when they were born, what title(s) they hold, who they’re married to, children, relationships to other peers, etc. For example, under ‘Westminster, Duke of’ it will give details of when the title was created, who has held it and who holds it now.
Also, ‘twerp’ and ‘berk’ (also spelt as ‘burk’) are both terms of abuse, with ‘twerp’ being relatively innocent, but with ‘berk’ coming from the Cockney rhyming slang for ‘Berkshire Hunt’, meaning ‘cunt’.