I have read the Harry Bosch Novels all the way thorough several times excepting a few of the weaker ones like Nine Dragons and The Overlook.
The only mystery Series I like better is Philip Kerr's Bernie Gunther series. I feel qualified to weigh in on Bosch as both a Cop show and more importantly in relation to the source material.
The thing that jumps out to me the most is that Titus Welliver's depiction of Bosch is similar to the older Bosch of Echo Park and Burning Room, and works with the book story-lines of the older Bosch in those, but is jarring when used in the Concrete Blonde, Trunk Music and Darkness More than Night story lines that are intertwined with those of the later books...Connlley successfully moves Bosch from action cop to more investigative cop as the books progress, but the show does not do this as well, so for instance the gradual comfort Bosch grows to attain with technology is weird because he flips back and forth from luddite to tech savvy incongruously; also ,missing is are the practical jokes from the books like the radio Hi Jinks from Concrete Blonde... "over and out dream leader!" and Bosch's pranks on Jerry Edgar, etc...
As a TV show Bosch seems more like a more modern version of The Shield than anything else, except Harry is not as morally bankrupt and despicable as Vic Mackey...and of course like all prestige TV since breaking Bad and The Wire, the pacing is excellent, and it looks like a film not TV
Casting Opinions:
Bosch; I always pictured Harry Bosch as looking a little like Anthony Bourdain, only with a mustache and curly hair, or maybe James Woods with more physicality. Welliver is a great facial and vocal actor, but he just seems out of shape and rotund for "wiry" Harry Bosch
Jerry Edgar; big miss, and PC concerns about a minority character in modern Hollywood are probably why the occasional laziness and self serving aspects of Jerry Edgar in the books are omitted. Actually Lance Riddick may have been better for Jerry Edgar
Irvin Irving: This is one place where the show is better than the book, the character of Irvin is less cartoonish and really explored well. He is no longer the villain of many stories, the shows lets the killers be the villains, but the way that the writing shows both Irving's decency AND ambition is excellent!
Maddie: annoying in both the books and the show, but hey 13 year old girls act this way a lot in real life sooo...ok
Eleanor Wish. Another miss, she doesn't seem like she could have ever been a FBI agent. and is just missing that edge...the show never explores her obsession with poker... replacing the juice she got from police work, and also, she spent time in prison, and the angst of her ruining her law enforcement career. The show really misses the Rachel Walling Character/ they are hopefully saving her for upcoming seasons.
Kizmin Rider: really missed, a very important character in the books, marginal here.
In summary, good show, missed the mark in some key areas, but a must see if you are a fan of the Books