I'm a big fan of the Podcasts - having subscribed to series 2 and 3 on Audible and thoroughly enjoyed them. Yes, they're very formulaic now but no worse for that - in fact that's the point. The main problem with the World of Karl Pilkington is that it will appeal mainly to the fans of the podcasts, but that audience will perhaps be the most underwhelmed of any reader. The reason is that the book offers very, very little new material.
Comedy spin-off books tend to be either comedy books in their own right containing entirely new, original material (Goodies, New Statesman, Vic Reeves, John Shuttleworth, Young Ones for example) or are pure transcriptions (Porridge, Morcambe & Wise, Rising Damp). The World of Karl Pilkington is better suited to the former but I'm afraid is much more of the latter variety.
I had hoped and expected this book to mainly contain new, previously unbroadcast inane and obtuse musings from the spherical headed sage, with unseen extracts from his diary and fresh Da Vinciesque theories sketched out in his own childish hand (perhaps in an unsavoury faecal medium). Instead the bulk of the book comprises selected transcriptions of the podcasts (in miniscule typeface with massive line spacing on horrible glossy paper).
Script books can be enjoyable but are always ultimately lacking for obvious reasons. Watching Hancock, Barker, Fisher or Rossiter bring scripts and characters to life with their genius performances is superb. But you can still appreciate a Galton & Simpson, Clement & La Frenais, Ian Pattison or Eric Chappell script read cold since it evokes pretty well the performance you're familiar with.
That's where material like the Podcasts falls down: the comedy is almost entirely reliant upon the performance itself and no transcription (especially heavily abridged transcriptions as these are) can do it justice. The immediacy, interplay, context, pauses, corpsing and nuance are all lost. In fact the converse is really true of transcriptions of ad-libbed, dynamic material like this: familiarity with a sit-com can help bring a script to life when you read it yourself whereas familiarity with the podcasts just makes the transcripts feel more lifeless.