Adonara is the first island east of Flores, off the coast at Larantuka. It is dominated by the cone of Ile Boleng, an active volcano. The main town on the island is Waiwerang and there are numerous villages spread along the coast and up the hills. The locals are predominantly Catholic, with a few Muslims in Waiwerang. The local language is Lamaholot with most people also speaking Indonesian. Very few people will speak English.
Very few foreigners visit this part of Indonesia and if you are Caucasian, by the time you reach Adonara the "Halo Misteeeerrr" cacophony (applicable both for men and women) will only intensify. The locals mean well and the place is as safe as any. Just smile and waive.
If you want to visit the westernmost part of Adonara you can get a small fishing boat to take you across the narrow straight from Larantuka.
Ojeks will meet you at the ferry. There are bemos plying the paved roads.
Climb Ile Boleng. There are trails up from at least four different villages. Expect to pay at least 20000 rp one way from Waiwerang to Lamalota or Lamahelan. See Gunung Bagging for good information.
The village of Lamahelan is a good place to visit. The locals hold on to their ancient traditions and there are many sacred objects around the village so be careful what you touch. Ask to see the centuries old huge elephant tusk (no touching, no photography).
Monday and Thursday are market days in Waiwerang attracting people from nearby islands.
There are a couple of budget accommodation options close the harbour in Waiwerang. In the villages you will have to ask someone to stay over.
Telkomsel has good gprs and 3g coverage. There is a post office and ATMs in Waiwerang.