My house IBI bill went from 280 ish to 408 euros, it went up 50%. I think the general increase was 50% in the Manilva area. Other areas have had a similar increase. So if yours has gone up by 100% check it out. There may have been penalties added, check the line items that make up the bill.
The reason I was told there was an increase was because the previous administration was over staffed and had used all the budget in the first 6 months.
Compared to what I pay for council tax in the UK I think it is not unreasonable. I know we have community fees but you would also have them in the UK if you lived in flat complex or a refurbished mill etc.