Fairly easy to put together. No instructions included but a quick look around made it easy to figure out,(make sure to check the 'inside/underside' of couch for the legs). Couch is indeed firm. Firmer than I've ever experienced, but I don't necessarily hate it. It's for our more formal dining room and I expect I'll get used to it (The couch I used to have was verrrry plush and I'm getting rid of it so..maybe I'll like firmer better!) It looks very nice and sleek, and I like the fabric (seems easy to clean). 
Since this is a sleeper sofa and the way the back is created, be aware that this is not a couch you want the back 'facing' a public area. It doesn't look good due to the fact it needs extra support when you lay the couch down, and that support is not 'aesthetic'. Glad we didn't plan for ours to be facing a public area. Overall I like this at the price point and expect it'll be a good couch for a few years.