The Icelandic alphabet is a Latin-script alphabet including some letters duplicated with acute accents. In addition to that, it includes the letter eth (Ðð), transliterated as d, and the runic letter thorn (Þþ), transliterated as th (see picture). Ææ and Öö are considered letters in their own right and not a ligature or diacritical version of their respective letters.
Icelanders call the ten extra letters not in the English alphabet, especially thorn and eth, séríslenskur ("specifically Icelandic" or "uniquely Icelandic"), although they are not. Eth is also used in Faroese, and while thorn is no longer used in any other living language, it was used in many historical languages, including Old English.
Sometimes the glyphs are simplified when handwritten, for example, æ may be written as ae, which can make it easier to write cursively.
The letters a, á, e, é, i, í, o, ó, u, ú, y, ý, æ and ö are considered vowels, and the remainder are consonants.
Icelandic vowels may be either long or short, but this distinction is only relevant in stressed syllables: unstressed vowels are neutral in quantitative aspect. The vowel length is determined by the consonants that follow the vowel: if there is only one consonant, the vowel is long; if there are more than one, the vowel is short.
The letters C, Q, and W are only used in Icelandic words of foreign origin and some proper names that are also of foreign origin. The letter Z is no longer used in Icelandic. The only place you might find this letter is in historic names of structures, organizations, etc.
In pronunciation, there are no silent letters in Icelandic. There are a few exceptions in spoken language where a letter might produce a different sound than usual. Otherwise, Icelandic is a very phonetic language.