Kangaroo Islandis on most Australian tourist documents, because of its name of course, and because you can see lot of marsupials living here. However, anyone who spends any time in Australia quickly realises that you don't have to go to Kangaroo Island to see kangaroos.
Having said that, I remember it as a very beautiful island, which, if you go there in the low season, feels quite isolated, with wonderful landscapes that are typical of south Australia: rugged coastline, beautiful beaches and eucalyptus forests. There are also sea lions in some of the coves around the island.
If you want to go there I recommend camping, as the tourist infrastructure is quite well developed, which will allow you to explore the island more.
This island, home to 4500 people, is rather peaceful apart from in summer, when the place becomes a popular destination for Adelaide residents. The landscapes are typical of the south, even becoming arid in the summer. There is not much woodland on the island.
Its beaches, which are both rocky and sandy, are among the most beautiful in Australia. The Vivonne Bay, on the south of the island, was voted Australia's most beautiful beach by the Australian people in 2003. As for me, my favourites were Pennington Bay and the beach hidden at the end of the Snake Lagoon walking route west of the island. The one slight drawback is the 'freak waves' sign, which advises against swimming for any walkers looking for a bit of refreshment.
Slightly calmer, the beaches on the northern coast are suitable for a whole range of activities (diving, sailing, kayaking etc.) However, as soon as you pass Cape Borda on the west, the seas get rougher. It's hard to go swimming without worrying about a treacherous current sweeping you away... or a shark! You will come across some other, more gentle animals on Kangaroo Island: wallabies, koalas, possums or even echidnas. Seal Bay is also a paradise for Australian sea lions.