The first time I had a moment like this, I was reading Twilight. James was attacking Bella and I was thinking all the time "God let Edward get there on time" I couldn't read fast enought to calm myself down (and I usually read really fast,LOL).
Next time was on New Moon, Bella was about to jump off the cliff and I was thinking "Why did Edward have to go, she wouldn't be doing this, When is he coming back???" I had another one reading New Moon and it was when Bella is running to save Edward, I was reading so fast thinking "Please Bella don't fall, run faster" New Moon almost gave a hard attack (LOL) While Edward, Bella and Alice, where with the Volturi, I was reading so fast that I wasn't actually blinking (it was my mom who notice that I wasn't blinking and told me "Please stop reading and blink), I remember I was so scare all the time, I didn't calm myslef down until they were back to Forks.
Eclipse: Where should I start???? (LOL). First time I started to read fast, becuase of course I wanted to read what was going to happen, was Bella comes home after Alice took her for the weekend and she founds out that someone was on her room, when Edward said to her that another vampire was there I was "OMG, I have to read faster".
During the night that Edward, Bella and Jacon stay all together on the tent, I couldn't stop reading during the part they were talking.
Then during the fight, I was reading fast again, my heart was about to stop all the time.
Breaking Dawn have me without sleeping, reading all the time and barely stoping for the 2 days that took me read the book for the first time. It was heart stopping all the time, it was amazing.