It's a fairly useless spell, that gives a bonus to jump (if you didn't know that already or you could not guess from the name of the spell). For giggles I switched out a level 1 spell that I wasn't using and instead of getting nightshield I got jump. On paper Jump adds nothing of real value so for stat boosting it is utterly worthless. But after I got Jump I realized how much of a difference mobility makes in a real time game.
Before, my primary means of dealing with mobs (I'm level 9) was to cast firewall, block and hope my stoneskin lasts or the healer keeps me from dying because all the aggro is suddenly on me (100 dmg per second ensures that). This worked well, I would leave dungeons alive and with more than half of the party's kills to my credit but stone skin is costly to cast and I don't have the life to tank like that. I could cast a wall and run but the baddies always follow and leave the burning wall area.
Now, I jump. Like some bizarre arcane bunny I hop about the area of the wall and suddenly I'm taking less hits, far less hits. In the same encounter (pack of wights) I went from nearly dying (pre-jump spell) to escaping while only having my stone skin worn down by half. Trapped in a corner? Jump, flanked? Jump. Drill Sergent saying jump? ask how high. I've jumped over fire balls, rays, projectiles and of course traps.
I'm not saying everyone should get jump or that is has magical powers that will make you an uber-sorc, I'm just sharing my personal experiences with the Jump spell. You may want to give it a try, if nothing else it's fun.