Very similar to Czech, and sharing the same alphabetic conventions, even to I and Y being pronounced the same except that I palatalizes some previous consonants.

Letters peculiar to Slovak are Ä, now pronounced the same as E; L-hook for a palatal L; Ô pronounced WO; and L-acute and R-acute for long syllabic resonants. These long L and R are the last survivors in Indo-European languages of rare sounds believed to have been in the ancestral Proto-Indo-European.

Here are the Unicode numbers for the letters that can't be expressed in HTML (extracted from my Using Unicode in HTML):

Č  Č   č  č   C-hacek
Ď  Ď   ď  ď   D-hook
Ĺ  Ĺ   ĺ  ĺ   L-acute
Ľ  Ľ   ľ  ľ   L-apostrophe
Ň  Ň   ň  ň   N-hacek
Ŕ  Ŕ   ŕ  ŕ   R-acute
Š  Š   š  š   S-hacek
Ť  Ť   ť  ť   T-hook
Ž  Ž   ž  ž   Z-hacek