It's spelled S-H-I-E-B-E-R, and pronounced shee-ber. No "c". Not "ei". Not shy-ber. Not "Schreiber", the name of my near-namesake at Harvard.
It is frequently misspelled, because it is close to being consistent with German orthography, the "ie" being pronounced as a long "e", though the initial consonant would then be spelled "sch". Nonetheless, there is no "c" in the name. Why? Because it is not a German name.
The name is an American invention, applied to my ancestors upon immigration to the US from the city Szczebrzeszyn, currently a part of Poland, and mapped below. During the immigration process, the surname was shortened from the city name, probably from its Yiddish pronunciation shebreshin.