[sdiy] starter components -- one of everything?

[Johannes Öberg]

I realized that what I'm looking for is probably a book on the
subject... I found
http://home1.gte.net/res0658s/electronics/parts_subs.html  but I would
like to learn _why_ some parts can replace each other while others
can't. Maybe I'm looking for an (on-line, preferably) electronics book
just above the basic "what's a diode?" level :-) Anybody have anything
to recommend?

/Johannes