1960s sci-fi novel with "tanks" for 15-minute or half-hour immersion for relaxation purposes (but is addictive)

Question

This is a relatively thick (+200 pages long) novel which appeared at least in paperback form in the 1960s, available in public schools. It includes such familiar tropes as future society, space travel, etc. - but I can distinctly remember only two significant tropes:

1. There are private (household) facilities in most upper-class homes where a person can immerse himself for 15 minutes in a sort of amniotic fluid, while a machine takes over his life processes (respiration, blood circulation) that is supposed to be very relaxing and pleasant. At the conclusion of the period, a computer voice "awakens" the subject person. There are also public versions of the same, where the immersion lasts 30 minutes (thus heightening the danger of psychological addiction).

2. Women can voluntarily undergo (expensive) cosmetic surgery in which prosthetic body parts (e.g., colorful plastic shells for ears) are implanted. One such high-class woman gets thrashed by a thug, and her prosthetics (not designed to take such physical abuse) are damaged.

Answer 1

I wonder if this is To Open the Sky by Robert Silverberg.

I was going to post the cover in case that jogged your memory, but the book appears ti have been published with multiple different covers. You can see various of the covers used on the ISFDB entry for the book.

It has tanks similar to the ones you describe. The book calls them Nothing Chambers and says about them:

Half an hour in a Nothing Chamber restored a man to vitality, draining the poisons of fatigue from his body and mind. Three hours in it left him limp, flaccid-willed. A twenty-four-hour stint could make any man a puppet.

Kirby lay in a warm nutrient bath, ears plugged, eyes capped, feed-lines bringing air to his lungs. There was nothing like crawling back into the womb for a while when the world was too much with you.

The cosmetic surgery you remember is a closer match and in particular the plastic ears. The book includes this scene:

Kirby bit his lip in anguish. A girl in the pew just in front of theirs turned around and said in a low, urgent voice, “Please. Please—just listen.”

She was such a numbing sight that even Weiner was struck dumb for once. The Martian gasped in shock. Kirby, who had seen surgically altered women before, scarcely reacted at all. Iridescent cups covered the openings where her ears had been. An opal was mounted in the bone of her forehead. Her eyelids were of gleaming foil. The surgeons had done things to her nostrils, to her lips. Perhaps she had been in some terrible accident. More likely she had had herself maimed for cosmetic purposes.

The book was published in 1967 so it matched your time frame (the Google Books article I've linked gives the date as 1999 but I think this must be the date of a rerelease).