Here is a partial list of some good books in English on Rosh Hashonoh.
The Artscroll Rosh Hashonoh Machzor (Holiday Prayer Book)
The Artscroll Mesorah Rosh Hashonoh
Companion Guide to the Rosh Hashonoh Prayer Service
The Survival Kit for Rosh Hashonoh and Yom Kippur
Days of Awe, Days of Joy — Hasidic Insights into the Festivals of the month of Tishri.
Menoras Hamaor — The Ten Days of Teshuvah (Repentance)
Sefer Hachinuch for the Month of Tishri.
Sound of the Great Shofar (semi-advanced)
Before Hashem You Shall be Purified (advanced, very intellectual)
Days of Awe (very advanced)
A good place to buy them is at store called Tiferes Stam, at (718) 336-6866, or 1-800-45-Torah. Ask for their catalog. (Their web page isn’t finished yet.) They ship worldwide. I trust the owner there.
May we all be granted a good and sweet year, a year of life and blessings.