More particularly.
a) How it can best be implemented
b) If it's possible/feasible
c) How much exactly is a UBI?
It would be great if there was an interesting book about this topic from which I can read the above.
I can recommend „Utopia for Realists“, granted it only touches on UBI, but it offers historic insights on feasibility and examples of implementation
One old post from him is a detailed plan for paying for it: https://www.scottsantens.com/how-to-reform-welfare-and-taxes... It's not a plan I support, but it is not an unreasonable set of notions.
For me, I would view UBI as a way to transition off of bureaucratic control of people's lives. The simplest in my mind would be a flat 10% income tax for it which would then be divided up equally across to all citizens, leading to about $6,000 (20 trillion economy, 10% is 2 trillion, divided across 330 million) a year and a break even at about $60,000 in income. While $6,000 may not sound like a lot, if one were to share living costs with three other people, then that is $24,000 in cash and there are plenty of places in this country (I live in a metro that is such a place) where one could live on that amount, potentially revitalizing less crowded places. When you factor in the fact that one can work without losing it, unlike welfare, then it becomes plausible to see it as a stepping stone to being more productive without being too much of a hindrance. If there is to be a social safety net, this seems the least damaging.
The concept of UBI is not a clear proposal without the funding mechanism. Many proponents unfortunately talk about the paying out without figuring out how to pay in. The recent attempt with the child tax credit increase, for example, was part of a time period of massive deficit spending and led to inflation, undercutting much of the benefit. MMT + UBI would be a feel good path to economic devastation.
A related idea would be to also eliminate public schools and convert that already property taxed money to direct payments to families of children. In my city, we spend about 16k per student. A quarter of that is for special needs so setting that aside, we would have 12k for the typical child. Funding children instead of bureaucrats. Grouping 20 children would lead to 240k which could easily fund 4 full-time teachers / staff for 40k each with 80k leftover for space costs. Compare this to 30 students per classroom in a decrepit buildings as is the case in my school district with documented, horrible failed learning outcomes.
The ultimate goal for me is the elimination of the government, but getting from here to there in a stable fashion is difficult. My thought is that simple, direct cash payments is a way to eliminate the bureaucrats, try to heal the harms caused by a century of economic government meddling, and eventually lead to a populace that doesn't think it needs a nanny state.
I like the book for because unlike a lot of more modern socialists, they make comparison all the time between their system and the USSR to explain why the latter failed and the former won’t.
If you only read one, read "Welfare for Markets" by Jager/Zamora.
Problem is, as things stand in almost all countries, (beside some oil-producing states), governments need to raise the money with taxes and it is a very high burden to get a non-trivial amount. States often can barely collect enough for pensions and to contribute to various forms of insurance (disability, unemployment and most importantly healthcare).
Now, proponents suggest scrapping existing social programs and replacing them with the UBI, but it will cost more and some people will actually much worse off.
Most existing social programs in the developed world are limited eligibility (means tested), so you have to prove your need to take advantage. This keeps costs low, although there are people who believe that i.e. requiring recepients be above a certain age, or to be children requires a huge and expensive administrative apparatus. This of course depends on implementation, but the point is means-tested programs became dominant across the world because they save money.
Now, about the point they don't always help, here is a simple example - will a 2-3 thousand dollars a month of UBI be enough to cover heart surgery? You could say people should buy health insurance, but to keep costs low you need to force people to buy it, and thus return to the typical national health insurance schemes around the world.
A more cynical person might think that many of the people proposing UBI are actually more interested in scrapping existing social safety nets than having a better working alternative.