Maybe John Nunn's Chess Puzzle Book? I'll give you a link to Coach Heisman's site. That's the only one he lists as being very difficult. Of course if you really want to learn chess systematically and are willing to put in the hours, then Yusupov or Dvoretsky or Aagaard all have a series of no nonsense books that are designed to take you to master level.
http://danheisman.home.comcast.net/~danheisman/Events_Books/General_Book_Guide.htm
Hello,
I have a question regarding a tactics training. Recently, I have decided to start to learn chess systematically - which I have never really done so - as a kid I was included in some training groups but I got eventually kicked out all of them because of lack of interest. I was told that the best way to start is to polish the endgame skills and tactics, and after while include some strategy (I have reasonable knowledge of openings). I already got a good book on endgames, but I have no idea what tactics book would be appropriate for my level (my FIDE rating is around 2050 and I am fairly good in tactics though I miss the less obvious one; in my country, I simply cannot get a book appropriate for my level and I am not familiar with neither English nor Russian publications). Could someone of you here help me to find some? Either in English or in Russian?
Thank you,
Vít