is there only 1 or a few lounges, is there showers like in mad?

The main Iberia lounge at BCN is in Terminal B, towards the "M" gates and towards Terminal C. There might be another one dedicated to the MAD/BCN Shuttle (puente aereo). The main one is kind if hidden away, as you approach it looks/feels like you are going to exit back out of security in a corner; the door is to the left of the exits. Inside it is very roomy, with huge windows facing the inside of the departures terminal.

Both times I've been there, it has been virtually empty. Furniture is comfortable, there are tables/chairs and there are couches. There are 4 or 6 PCs with internet access, a smoking lounge, newspapers (mostly Spanish) and plenty of drink options including many types alcohol. Food options are more limited like packaged cookies, raisins, etc. General cleanliness only ok; bathrooms only ok. I didn't see any shower facilities but didn't ask either. Staff is cold as ice but will provide assistance if asked.

There is some info on the BA lounge here

It's definitely a lounge worth avoiding!

Well, I don't think it is at all that bad. It has the basics and is better than sitting out in the common areas and paying through the nose for drinks, coffee, alcohol, etc. There are PCs, televisions, newspapers, etc., and comfortable places to sit and use them. I don't see why there's so much hyperbole in that other thread. The times I've used it, between 10am and 1pm, it was a perfectly serviceable airport lounge.

Spot on. ^

It is an AWFUL lounge atleast as far as food options go IMHO. I flew BCN-LHR last weekend on a lunchtime flight, and I had missed brekkie due to having overslept. Thought I'd grab some food in the lounge! Well, the "food" in the lounge was crisps, olives and biscuits. And that was it. Nothing else, nada. Even the Spanair and the Priority Pass lounges at BCN have more choice.

The only english newspaper available was the FT. And the IB staff were chillier than the Arctic in December.