1.1.The book was much worse than any of his other books.
1.2.The book was much inferior than any of his other books. (X)
How about "The book was highly inferior to any of his other books."
2.1. He is the center of attention now, though a few years ago he was hardly known.
2.2. He is in the limelight now,
thoiugha few years ago he was hardknown.
Yes, but: "He is in the limelight now, though a few years ago he was hardly known."
3.1. I must confess that I did not find the story too exciting.
3.2. I must admit that I did not find the story too thrilling.
Both are correct.
4.1. We had taken it for granted that he would help us, but he didnít.
4.2. We had assumed that he would help us, but he didnít.
Both are correct.
5.1. He has gathered a good deal of information for his book.
5.2. He has accumulated a good deal of information for his book.
Both are correct. (Gathered is better, though. I think it's more active and suggestive of somewhat greater effort.)
6.1. I place everything in your charge.
6.2. I entrust everything to yours. (X)
I entrust everything to you.
7.1. It was a pleasure trip to look forward to.
7.2. It was a pleasure outing to look forward to. (?)
Rather odd...I wouldn't say it in a hundred years.
8.1. Our knowledge of the subject does not go that
8.2. Our knowledge of the subject does not cover all that. (?)
The only problem is that it sounds quite strange to me to say your knowledge of something doesn't cover something. Ordinarily, a book or a course does or does not cover something...in other words, that material is or is not included. We tend to think of someone's knowledge in terms of how far it extends; we tend to think of the material in a book or course in terms of what it covers.
Hope this helps.