BC&SL is, at least for me, the most depressing and darkest DT album written.
I mean, don't get me wrong, Scenes is also heavily dark and depressing but, after all, it's fiction.
What this album has is that it's real, and its stuff is about things that actually happened to Petrucci and Portnoy (Except for A Rite of Passage, which I consider to be a little out of place, although not a bad song).
Let's analyze the songs.
A Nightmare to Remember: The darkest one here, and talks about a tragedy, which even though it was not THAT severe (since nobody died and apparently nobody had permanent physical injuries), from a child's point of view, it's an horrific experience. Imagine looking at your family in such a terrible situation, moaning and calling for help or, even worse, not saying anything and then experiencing the incredibly frustrating sensation of not being able to help anyone while you are being treated and also, unaware of their current status!
A Rite of Passage: This one I have not heard it that much, but as far as the lyrics concern, it's one of DT's most interesting lyrical approach. I mean, don't judge me, but when I first heard it I thought of the Illuminati almost instantly, and it offers a pretty good atmosphere about secret organizations dealing with the initiation of its members. (Keep in mind I could be wrong about this one, since I'm not a great fan of it, just giving my opinion with the lyrics)
Wither: This one is quite relaxing, awesome, but also very depressing. It's basically John Petrucci telling us about his problems when writing. The inmense frustration he feels when he has to start over and get rid of stuff that simply didn't work, spending hours and hours working on it. Telling us that his brain will eventually run out of ideas and that he will have to spend sleepless nights thinking about what to write afterwards. This probably also applies to other group members.
Ever heard of Chicago song 25 or 6 to 4? Well, it's actually quite similar to Wither, a song about writing songs, dealing with the frustration of thinking over and over and throwing away a lot of ideas. (And no, it's not about drugs).
The Shattered Fortress: The journey of a man reaching its end, after years and years suffering with alcohol, he is finally free and forced to deal with the aftermath of what he has done, accepting himself the way he is and the fact that he has to understand everyone rather than to be understood. Learning from thousands upon thousands of mistakes before him and looking at the future, promising to be forever helpful of everyone around.
The Best of Times: Saddest one here. But the kind of sadness that is just plain depressing if we keep in mind a few things...
If we pay attention to the slow part of the song, it's basically a son being sorrowful and apologizing at his father for not being able to accomplish all their dreams, realizing that time just vanished, and that all those things he wished to do with his best friend and idol, are now gone forever. He comes to the conclusion that he has to live on, to honor his father's image, while remembering all they did together as two best friends. Now... This is sad because it was never performed live, since Portnoy never had the strength to do so... And who would blame him? It is also a song that could never be performed live now... Imagine how would Portnoy be if DT was to play this song without him... And to think he quit DT shortly afterwards... Which means his father passed away without learning about his son's departure from the band.
Now here comes something interesting. The Best of Times ending solo is, for me, John Petrucci's most emotional solo ever, and one of the most emotional solos ever written. Thus, it's DT's most emotional outro ever... Which fits perfectly for the following song...
The count of Tuscany: Most interesting one, and also another of the saddest, but this one has a sadness that is mostly instrumental, but also lyrics are important. Listen to the intro, it is so beautiful, and what a perfect way to continue what was set during The Best of Times. This is arguably the most emotional intro ever, it's simply awesome. Although neither The Best of Times nor The Count of Tuscany got DT's hardest instrumentals, they do hold some of their most emotive (For me, the most) moments.
The Count of Tuscany sounds so joyful, it is not a sad song (For the first half), but rather exciting and happy, yet in depth feeling so... unreal, so depressing.
The lyrics basically speak about a man meeting two strangers, and believing that they are going to kill him. Only to find out that it was a terrible confusion. The middle part which everyone hates (The calm one) fits perfectly to the situation, it's awesome if you think about it. I prefer to see it as a man struggling to deal with the fact that he is going to die there, alone, with nobody noticing. The man goes on, thinking and thinking before finally collapsing and continuing the lyrics... James' voice reflects that so perfectly... And then... The best part kicks in... The man, the Count, had invited him to see his place, excited, to tell someone about his stories and traidionts... Only to find out he has freaked out his guest. Then he tries to fix things, explaining everything, saddened over the fact that his "friend" wants to leave... Before finally agreeing and telling him "Of course, you're free to go... But tell everyone about me and my brother...". I like to see it as the man and the count coming into terms and the man promising the count to narrate his story afterwards, and reveal their lifestyle and popularizing the isolation in which he must have been living...
Well... These are my opinions... man, what a bible.