Parylene E, a low K polymer thin film, with the approximate composition 69% diethylated and 25% monoethylated poly(p-xylylene), has been chemical vapor deposited via a cyclophane precursor at room temperature. It has a dielectric constant of 2.34 +/- 0.03 and dielectric loss of < 0.005 at 10 kHz from MIMCAP structures. It is particularly unique compared to the other common parylene polymers. Namely, it is nearly optically isotropic and it is soluble in common laboratory solvents such as methylene chloride, chloroform, and toluene. It is shown to have an optical birefringence of -0.0112 at 634.1 nm and a correspondingly low degree of crystallization after a 150degreesC postdeposition anneal. The low degree of crystallization results in a smooth film (10 Angstrom rms surface roughness for a 2060 Angstrom thin film) with no optical loss (in reflection mode), i.e., an extinction coefficient of zero. These properties for parylene E make it appropriate for use as an optical waveguide and for archival conservation or other applications where low optical loss or film removal might be necessary.