B:T-F/SYO details the origins of two of the top 10 (in my opinion) members of Batman's Rogues Gallery. While a newcomer to comics might find this comprehensive, a long-time fan might find themselves let down (for me, it was with the Two-Face story). The book begins with the origins of Jonathan Crane/the Scarecrow, as one of the new brand of criminals to hit Gotham, commonly referred to as "freaks". It gives a well-detailed account - through flashbacks - of his life, and how he came to be the pre-imminent 'master of fear'. Like most psychos, his life is one of trial and tribulation, born out of a troubled/tortured childhood. The bastard son of a young junkie mother and an architect, he was born weak and spindly, unwanted by either of his parents and maternal grandmother; left in the care of his frightful great-grandmother and raised in her all-but dilapidated Georgian mansion (reminiscent of Disneyland's Haunted Mansion). His story would make one almost feel sorry for him as it explains the origin of his fear of birds, a few ways by which he would have chosen his future monicker, his dismissal from the university for his dangerous teaching methods, and his dabbling in the chemical sciences to inflict fear on his victims. A well-compiled story that satisfies on all counts, even if to a more researched fan it comes up wanting in some places.
I personally was not a fan of this take on the origins of Batman's most bifurcated foe: Harvey Dent/Two-Face. What this story does is it tries to capitalize on the success of the graphic novel Batman: The Long Halloween, and weaves a lot of that story into this one and puts its own slant on it. Sadly, it makes a promise it cannot deliver. It does not explain Harvey's troubled past with his abusive/alcoholic father, makes no mention of how his split personality might have developed (besides arising out of his scarring), and most importantly does not explain the origin/significance of his coin. It introduces several characters that were not present in TLH, most of which - while occasionally interesting - didn't do much to help the story. Also, following Dent's transformation into Two-Face, there is a scene that gives an account of the origin of the giant penny in the trophy wing of the Bat-Cave that falls just as flat with the inclusion of Joe Coyne/the Penny Plunderer (see episode #35 of Batman: The Animated Series "Almost Got 'Im" for a far superior version of the 'Penny Trophy' origin story (Batman - The Complete Animated Series)). Because it alludes to TLH, much of that story is not included, so anyone who hasn't read it would not get the few-and-far-between references which even then seem out of place. This comic ought to be taken as its own entity and it's a shame a masterpiece like TLH had to get dragged down with it.
In all frankness, if you can find the two-part Scarecrow story separate from Two-Face, then it is worth the purchase; if not, then still get it.