You asked what interesting about Harry Potter book I've read lately. Here's my opinion about nice Snape:
My last, but the most convincing for me version of what had happened:
1. DD finds the ring and there's a curse put on it, so he rushes off to Snape and he saves his life.
2 Narcissa and Bellatrix go to visit Snape and he is forced to make the Unbreakable Vow, if he hadn't done it, he wouldn't have been trusted. He doesn't tell the whole truth and I think that's the way he's convincing to Voldemort. He tells the truth, but not on the whole... for example he says that DD suffered an injury last month which isn't true, he suffered it earlier... or that Harry isn't a special boy because he's no good at Dark Arts (so what if he's good at something else). Snape should be a politician
3. DD knows about the vow from Snape and they know that: if Snape doesn't fulfill it, will be dead and Draco will be dead, if Snape helps Draco and kills DD, both Draco and Snape will be saved and Snape will be LV's most trusted servant. Remember that Snape told the Order about Harry in the ministry and if his orders were to stay behind, as he said, LV didn't know that Harry had told Snape earlier about what he saw.
4. Bellatrix is jealous because she'd want to be the most appreciated LV's servant. She doesn't trust Snape still and teaches Draco Occlumency.
5. DD goes to Slughorn to give him Potions job, he knows about the DADA curse, but he also knows that Draco will try to kill him throughout the year, so Snape isn't needed at school all year, he may give him DADA job to sweeten his hard life
6. Draco doesn't want to tell Snape what he's up to, tries to kill DD by using necklace and poisoned mead. He doesn't want to kill DD face to face and it's no good for the students.
7.The quarell in the forest is maybe because DD is worried about the students and Snape tells he doesn't want to do this anymore... to protect Draco? Remember that Draco and Snape had quarelled before and Draco wasn't nice to Snape as he used to be. Snape might have become pissed because he had to do such a difficult thing- kill DD if there's a need- and Draco shouted at him.
8. Both DD and Snape know that Draco wants to kill DD but they didn't know about the Vanishing Cabinet and the possibility it brings: you can take more Death Eaters with you, it's more dangerous.
9. When DD and Harry go to find a Horcrux, Draco sees a possibility to finally bring Death eaters, he mended what he had to mend and that's a DD's mistake- he didn't appreciate Draco's attempts and Harry's clues.
10. They go to the cave and there's another DD's mistake- the Horcrux is false.
11. DD is weakened and he asks Harry to fetch Snape because he's good at antidotes... Then Rosmerta tells them about the Dark Mark and DD hurries to the castle, he thinks that somebody from the school was killed. He didn't know about the Death Eaters and still asked Harry for Snape.
12. When DD sees Draco's coming, he immobilizes Harry, it's the final scene that he expected. He didn't want Harry to disturb. He tries to find out what Draco's up to, so that's why they chat, he knows that Snape should finally come as he had to spy Draco. He tries to convince Draco to come to the right side and promises him hiding.
13. It could work! But unfortunately Draco took Death Eaters with him, so they see he can't kill DD. There wasn't much time.
14. Finally Snape comes and looks what's going on. He sees Death Eaters, a frightened Draco, and Death Eaters tell him Draco can't do it - and they'd voluntarily do it for Draco- but Snape has to do it to save Draco and himself, Dumbledore is half-dead unfortunately, and he pleads... to kill him? How could he plead: save me, Severus, and please give me some antidote: near Death Eaters?
15. So I guess there were unexpected things in DD's plan. First of all, Death eaters with Draco, as DD firmly believed the castle is well protected.
16. Snape runs with Draco, he doesn't kill anyone and doesn't let to harm Harry. I'm not sure if he really gives Harry advices about keeping his mouth shut and mind closed, because it's during their fight and simply Snape knows everything what Harry wants to conjure becaus ehe's not good at non-verbal spells and Occlumency.
17. He's angry when Harry calls him coward because he risks a lot, all people will hate him like Judas. It's possible that somebody in his past called him a coward- his father?- and he wants to prove he isn't.
18. The rest of the order doesn't know about what they had planned... But there are ways to prove that Snape was ordered to do it and I think they'll find out. If DD told the order that if he had to die, he'd die, they'd protest and broke the plan.
19. DD during all schoolyear was teaching Harry about LV, his behaviour and Horcruxes and that he must fight LV himself.
I also have a story about bad Snape, I'll search for it later. And here's a picture story I love and have as my avatar now: