The Eve Mattress
Neither a mail-order mattress, nor a mattress-in-a-box, nor a relatively cheap mattress sounds like it would pair well with a good night's sleep. Still, the makers of Eve promise their 3-layer technology will deliver the sweetest ZZZs you've ever had. And if, after a 100-night trial, you don't agree, they'll refund ever dollar you paid them and schedule a free pickup for return, no questions asked. The mattress also comes with a 10-year guarantee.
In case you're wondering, no, as far as I know these makers of Eve are not God. But I'll bet if you love their mattress as much as they think you will, you'll call them a godsend.
Eve mattress composition starts with a high-density foam base, and stacks that with a mid-layer of high-resilience comfort memory foam, followed by a new-generation memory foam topper. Then the whole mattress is wrapped in a cover "lovingly hand-knitted in the UK." (Probably by Eve employees' grandmas. Something to keep them busy in retirement, you know, give them a few extra pounds to put on the horsies at Newmarket.) In total, the mattress is 10" thick. You can place it on bed slats or a box spring, or just set up sleep shop on the floor.
Eve is able to maintain quality without a proportionate increase in cost through direct online ordering--cutting out middleman retailers--and compressed-in-a-box shipping. They achieve the latter through rolling and vacuum packing tech that squashes the mattress into a manageable rectangular house of cardboard. The compact size and more normal dimensions of the box both reduce shipping costs, and make the mattress much easier for you to receive and unpack yourself.
Eve setup should be fairly easy too. Once removed from the box, haul it where you want it, remove the plastic, and watch the mattress grow magic-animal-in-a-capsule-style right in front of you. It will be ready to rock you to sleep in a few minutes, and reach its full size in 1 to 2 hours.
Eve mattress come in sizes Twin, Twin XL, Full, King, Queen, and California King.