Can I Take Skill Points Back Once Used?

If I put points in, say, Blood Magic, then later find I prefer Death Magic, can I transfer the points, or is my choice permanent?

No you can switch them around.

You have 24 refund point that can be used to lower an attribute by one each. This frees the attribute points to be used elsewhere. Refund points can be regained at a rate of one/250 XP

Skill points are what you need for buying skills. You can't put skill points into Blood Magic or Death Magic.
Attribute points are what you spend on attributes such as Blood Magic and Death Magic.
As already stated, you get one refund point every 250XP, to a maximum of 24 refund points at any time. You can use these to take points back out of attributes and then you can put them into other ones.

To better explain... there is an up and down arrow beside each skill... you can transfer (place or remove) points using those arrows.