These are not the best of times for small business. High interest rates, unemployment and a decrease in consumer spending have helped to paint a dismal picture for the private sector.

Yet while the growth rate of the federal budget has been substantially reduced under President Reagan, the actual amount of funds available to business each year through loans, grants and other forms of assistance remains quite high. The question arises as to why more businesses don't take advantage of this resource, and the answer, in too many cases unfortunately, is ignorance. Many businesses eligible for government help are either unaware that such aid exists, or, being aware, have no idea how to go about securing some of this assistance.

N. H. and S. K. Mager try to eliminate this stumbling block with their book "What Business Can Get From the Government," (Boardroom Books, 1982, 657pp., $75), a thorough, well-researched guide to the myriad sources of assistance provided to small business by the U.S. government.

Judging the book by its title might very well elicit some amusing comments from the skeptics, but for those interested enough to invest the $75, the book will prove to be an invaluable guide to the wheres and hows of tapping federal assistance.

The Magers, a husband-wife team who have compiled and edited over one hundred business information books, acknowledge that there have been some changes in the nature of government supports for business under the Reagan administration. But, they say, "the structure of aid to business remains substantially as it has been for the past decade." Keeping in mind that "the United States government is the world's largest market, lending institution, and storehouse of information," a business would do well to include this guide in its reference library.

The book's logical, easy-to-comprehend format should appeal to the neophyte who has never attempted to enter the maze of government aid programs, and even old pros at this game will profit from its hints and suggestions.

Each of Section One's seven chapters deal with an aspect of selling to or buying from the U.S. government. Section Two, entitled "Special Assistance for Small Business", details the preferential treatment provided to small and disadvantaged businesses and to minority and women business owners. Section Three covers the broad area of general assistance to business, describing how to take advantage of the government's wealth of knowledge and know-how.

The final, and largest, section of the book lists examples of federal grants for specific programs. Although the authors concede that most federal grants are made to government or nonprofit organizations, they explain that "the actual work is often done by private industry and profit-making firms." This section will serve to generate ideas for the "imaginative and energetic entrepreneur" who learns to take advantage of this "flow-through" of funds.

The appendix includes addresses of regional, district and field offices of pertinent government agencies, as well as a list of commonly used abbreviations and acronyms.

The Magers don't try to fool you. They admit that there is no way around the paperwork or the homework involved in procuring aid from the government. But their book is a tool that will start you off in the right direction and see you through to the desired end.