1) This is the best book I have ever read. 2) This is the most difficult problem I have ever had. Well, "ever" means at any one time , so it's a tad redundant with "first" and "only", which also mean "one", and by semantic extention "ever" is redundant with "best" and "most" ("ever" means one thing, and best/most mean "top thing").
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1) This is the best book I have ever read.
2) This is the most difficult problem I have ever had.