Murray's book goes into detail about how much a program of guaranteed income for everyone would cost in the United States, and suggests some probable effects that would have on everyone's everyday behavior. I read the book a year or two after it was published.
Murray's own summary of his argument and reviews of his book may inform the discussion here. Big public policy proposals are not easy to discuss, but the big public policy proposal of a guaranteed basic income for all is a response to existing policy of supposedly targeted social welfare programs that are just about equally expensive in the benefits they provide, but much more costly to administer.
As a matter of personal opinion, I am still thinking about whether or not a basic income guarantee is a good idea, but I definitely want to figure out if spending no more in total for social welfare by directly transferring cash to all citizens would simplify administration of welfare programs and allow more individual choice about how to use the money.