There is no legal requirement for a "reading of the will." However, a will has no legal effect until the court admits the will to probate.
First, you can check with the probate court in the county where your father resided to determine if anybody has opened probate. Probate case files are open to the public viewing.
If not, you can apply to the court to open probate and petition the court to compel stepmother to produce the will. This is not a do-it-yourself project (particularly if the will ends up being contested). You would be best served by retaining an attorney.
Remember that many married couples own most assets jointly with right of survivorship. Or create mutual beneficiary designations for assets that are individually owned. The titling and beneficiary designations take precedence over the provisions of a will.