Other people also seem to have read "Challenger - A Major Malfunction" (1987) by Malcolm McConnell. This is an excellent book which contains a wealth of technical detail about the incident and the mechanics of the O-rings and their failure modes. Also a lot of stuff about Thiokol and the political background - I humbly suggest that you read it Lu.
For reasons not unconnected with my work I am also interested in the chain of events leading up to nasty accidents and the links are always much the same. Just as in the Turkish Airlines 981 DC-10 disaster there had been many indications for a long time that something was seriously amiss with a criticality 1 component. In both cases "fixes" were designed and applied in the hope that the patch would render the problem less critical, but quite a few people remained seriously concerned. The financial and time implications of a full redesign and retrofit were so great that this was judged impractical.
O-ring erosion (which wasn't supposed to occur AT ALL) occurred on virtually all launches after the lightweight SRB casing was introduced. It was known to be worse in for launches in cold weather when the cold-stiffened chromate putty failed to conduct the pressure of the ignition transient and correctly seat the O-rings. These problems became significantly worse after a preflight pressure test (which was supposed to check O-ring integity) was introduced. Quite a few people were extremely worried (e.g. Roger Boisjoly) and wrote scads of memos. Still, nothing blew up and O-ring erosion came to be accepted as almost normal. People consoled themselves that a new joint design was on the way. You know the rest.
Right from the start there were considerable worries about tile integity and bonding and these have grumbled on in the background since the first flights. Tile damage on launch wasn't supposed to occur. It did, and insulation loss from the big tank was known to be a primary culprit. I think a lot of people were pretty worried and held their breath for each re-entry. Still, nothing blew up and tile loss/damage can to be judged an acceptable risk.
To quote the late, great Richard Feynman (of the Rodgers Comission): "I read all of these reviews and they agonise whether they can go even though they have some blow-by in the seal or they had a cracked blade in the pump of one of the engines, whether they can go next time or this time and they decide yes. Then it flies and nothing happens"
"Then it is suggested, therefore, that the risk is no longer so high. For the next flight we can lower our standards a little bit because we got away with it this time....It is a kind of Russian roulette."
When you win, it just until the next time.
And when you lose, you lose bad.....