There were other small ones, but the ones that stood out:
Page 16, after black's Bc5 - not because of the explanation, but because of the fact that he thought for 20+ minutes in this position. I would not recognize this as a position where white needs a long think, as a matter of fact I would play a3 very quickly as it feels natural, but that's not necessarily good, as I would likely be oblivious to quite viable alternatives for white.
Pages 16-17, explanation after black's a5 - this one is just a gem IMO. Firstly, because I would play a5 instantly as black in this position, so it is super good to see a very clear explanation as to why it just isn't good and is more of an automatic move. Secondly, the explanation as to why the inclusion of a3 and a5 definitely favors white is so simple and clear that it's just fantastic and not something I think of during the game. Thirdly, a bit deeper explanation of the weaknesses created by a5 (it's not just b5 square, but the fact that the base of the pawn chain is likely going to be on b6, instead of a7 is also something I would likely not think about at all during the game.
Page 20, explanation before white's Be3 - the concept in itself is well known (even to me!), but the reason why I enjoyed it very much in this case is that before reading it I tried to put myself in Gelfand's shoes and approach the position after black's Qb3, and this concept came to my mind in a different fashion - black is underdeveloped, how can I punish him by active play? So I even started looking at crazy stuff like Nd5 and so on. I came up with Be3 as my move in a bit, but not through consciously trying to make use of that concept, but just cause I thought it creates some immediate problems for black. It was refreshing to see that it's kind of how Gelfand thought of it too, that the use of the concept was more subconscious than conscious - except I am not sure if I have it there in my subconsciousness at all
Well, I hope I do now!
Page 22 - "at this point I had to calculate that the knight endgame is winning", bro, what knight endgame?! Still four rooks on the board! Ooooooooooooh, that knight endgame... This one showed me how far ahead he is of me, as I would absolutely not be calculating any possible knight endgames in this position.
Page 23 - just the fact that this endgame is so obviously winning to him, while it is not so clear to me. I mean, I understand that white is much much better, but I would not dare to say it is winning. Now when I see it play out, it seems very obvious that it was easily winning all along.
Enough for now, I'll try to post others as I come along them, if I remember to do so.