My opinion (for what it's worth): Stranger in a Strange Land is probably the finest book ever written by Heinlein. The problem is not with this particular work but with his subsequent work. I always felt that, in most of his later efforts, it was the same character regurgitated which, to me, showed Heinlein's limitations. Paradoxically, Michael Moorcock made a career out of character regurgitation (The Eternal Champion) and it worked for him. I think the reason it worked was because Moorcock's was a conscious decision whereas Heinlein was probably working at his limits. Still, it's a fine book and worth persevering with.