It is an excellent mood stabilizer, mostly used for Bipolar disorder, excellent for BP-I's who have the tendency to have severe manic episodes vs. depressive ones.
BP-II's have milder manic episodes but can have severe, to fatal depressive episodes, this does not mean either types of bipolar do not risk fatal depression.
The books I have listed at the top of Bipolar forum have short to extensive chapters about Lithium, I can tell you a lot about it and it's origin but I'd gab your ear off
If it has been suggested to you to try, that is if this question pertains to you, it's worth a try, it doesn't make you sleepy and non functional (job wise) as many of the other mood stabilizers do. Lamictal is another good one for those with mild mania vs. full blown or escalating mania.
Please note I am just telling you my views on these medications that come from my own personal experience with taking them.
Please take care,

DE