> Well, what I meant is not that I mind long explanations of whys, but I
can't
> find any works that are not extremely specialised in nature, ..
Piotr has mentioned -and warned you about - Szemerenyi, which is (a) out of
line with the developing consensus in a few ways (b) extremely reliable (c)
full, detailed, and complex. Becasue of teh last point, it might not be
what you want.
Could I suggest instead any book which has an introductory chapter on PIE?
This might give you a quicker and less detailed overview of the subject.
There's a 7-page version in Baldi "An introduction to the IE languages" (Sth
Illinois U Press 1983), but this might be too small. Beekes "Comparative
IE LInguistics" has several chapters (about 130 pages) and this might be too
much - though it's still shorter than Szemerenyi.
Peter