I've never read the book - and most reviewers say don't bother!
The '47 film was superb and one can not compare a TV version of 180 minutes with a far shorter film. David Farrar was memorable, and his performance is matched by the current guy, who I suspect is of Italian origin, although married to Emily Mortimer. Professional TV critics in the UK have a very mixed range of stars and that indicates a very mixed range of talent. I suspect the older critics that saw the film will rate the TV series a lot lower than younger critics. For my part the writing and directing are both sub-standard, with ridiculous brief 3 seconds? flashbacks that have no dialogue or clues as to what is being shown. The last two episodes will not be watched by me.