Here is my personal opinion.
For Kindles I always recommend getting a warranty from Squaretrade. If you have a eink kindle the biggest problem is accidentally cracking the screen. This has happened on a number of kindle that I have purchased, both with and without covers. Amazon will usually replace the kindle for free during the first year, but after that they usually will only give you a discounted price on a refurbished kindle.
Squaretrade will give you the purchase price in either cash or Amazon gift card (with a 5% bonus). I always do the gift card.
Recently Squaretrade has raised the price of kindle warranties. I currently recommend a 3 year accidental damage warranty. If you buy it on Squaretrade’s website it is $69.99 for a Kindle Paperwhite which costs $119. You can usually get a 30% off coupon, but that is still $49. That is still 40% of the price of the kindle.
If you go to Amazon you can get the same warranty (3 years and accidental damage) for $26.99. Over the life of a kindle (I have purchase about 20 that I used or gave away to friends or family) I estimate there is a 50 percent change of damage, usually a cracked screen.
By the way, I do not recommend Squaretrade for warranties on cell phones. They always try to fix cell phones and it usually seems to take twice as long as what they promise and they don’t do a great job. But with Kindles Squaretrade doesn’t seem to have the facilities to fix the screen so they just give you the money.
If you do get a warranty from Squaretrade be sure to email them a copy of your receipt as soon as you buy the warranty. Because if you don’t email (or fax) them the receipt you have to have a copy of it before they will replace the kindle.