Thank you for your question and welcome to Just Answer.
Lumineers is a brand name of a special kind of veneer made of a patented porcelain material that is very tough and durable. For this reason, Lumineer veneers are made very thin, almost as thin as a contact lens, The advantage to a thin veneer is that very little, if any of the natural tooth has to be drilled down in order to place them on the teeth, so says the manufacturer. In reality, if you do not remove any tooth structure before cementing a thin shell of porcelain over the teeth, they will make the teeth thicker as they will "stick out" a bit. Lumineers cost about 75% to 100% of the cost of traditional veneers.
Traditional veneers are also made of porcelain but tend to be a bit thicker. Because of this, more tooth structure had to be removed in order to prevent the veneer from "sticking out" once cemented.
If you are considering veneers because you are unhappy with the shape and position of your teeth, then you want to go with traditional veneers. Changing the shape and position of your teeth will involve areas on the veneer that are thicker and wider in some areas than others, a trick you can not accomplish with contact lens thick Lumineers. If you just want to change the color of your teeth, then lumineers might be for you. Here are some links that will give you more information about Lumineers:
http://www.mynewsmile.com/cosmetic/Lumineers_cost.htm This is information explaining the shortcomings of Lumineers
http://www.cosmeticdentistryguide.co.uk/lumineers.html This is the Lumineer website that tells you how wonderful they are.
Take a look at both links and see what you think. I hope this answers your question.
If you have any concerns regarding this issue that I have not addressed, please let me know and I will get back to you with more information.
Sincerely, XXXXX XXXXX DDS