A couple problems with your question:

1) Why don't you just tell me the name of the books you've read so far ( a tip of the hat to Kramer)
2) What part of dotnet are you looking to read about, what language, etc.

Amazon has a rather good review system of books. I'd at least start looking for the 4/5 star books in the area you're interested in. There are several asp.net books that have quite a few reviews and have 4 1/2 stars.

I would just look at several highly rated books and read the table of contents to find books that cover the topics you don't feel 100% comfortable with yet.

>>I think there is a hugh difference between asking a beginner question such as "what's the purpose of an interface", vs. asking "what is an interface".
>>
>>There are very few descriptions of Inheritance in books that don't go into what an interface is. But it is also not clear from most books good guidelines for inheriting from a base class vs. implementing an interface.
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>>As the 2nd question shows some motivation on your part. Asking the first question shows you are trying to learn the language piecemeal. There's a very good possibility you don't know what polymorphism is. So most likely you're hoping for someone to basically write an entire chapter for you.
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>>Many people do that on-line for some, enforcing their lack of motivation. But I see more and more answers trying to help guide the original poster towards doing some basic reading before asking the "what is..." type of question.
>>
>
>What is the best beginner's .NET book in your opinion, then? I've read a few so far...