BibTeX, biblatex and biber ⇒ Unicode (greek) book title with Bibtex

[phi]

Anyway obviously Bibtex supports unicode cause at least now i have greek text in the title.

Neither BibTeX nor LaTeX support Unicode. LaTeX allows for some very basic UTF-8 input, but that is not real Unicode support. BibTeX and LaTeX have been created long before Unicode came into existence, and they have never been updated until now (and probably they will never be updated). If you want real Unicode support, use modern replacements like XeTeX/LuaTeX + biblatex + biber instead. BibTeX only knows about ASCII and lets every non-ASCII input pass through unmodified (and unsorted). You have Greek letters in your example because \textgreek switches to a font containing Greek glyphs in the ASCII range, but that again has nothing to do with Unicode.

[pipk]

Don't forget that the problem with Unicode and bibtex isn't really that it mangles it often. You can usually get round it using some macro like \greektext{} or character macros in general but this only "solves" part of the problem because then the sorting of your bibliography is completely broken. Say you have a name like:

AUTHOR = {\v{S}mith, Simon}

That gets you round the problem with Unicode characters in the .bib but "\v{S}" is never going to sort properly in your bibliography if you want the bib sorted by name at any point - it sorts as a string beginning with an ASCII "\". For this to really work, you need to be using a real Unicode backend engine with CLDR support and the only choice for that is biblatex+biber.