Howe's book is around the nets as pdf's if you look or cheap kindle downloads.
If you would compare modern gunsmithing books to that of Howe, you will find most of them remarkably devoid of details in the book as the run of the mill gunsmith today is not the artisan of the past. Thus, few engage in forging and making new parts, things like stocks from rough blanks have been farmed out to specialists, and those running full machine shops are rare. Part of the reason is that most people are not willing or cannot pay for the labor involved in doing gunsmithing the old timey way (for example, the resident gunsmiths at Williamburg, VA make the parts in period authentic ways and fit them on sight which takes weeks--the resultant firearms are priced then as such). A similar artist is Turnbull who painstakingly recreates the past. Reading such as Howe, Chapel, Dunlap, etc. will take you back to when labor was relatively cheap and firearms were treated as durable goods that lasted generations.
The major dangerous stuff is some of the old ways of heat treatment and bluing formulas. Howe is more careful than some of the others regarding things like heat treatment of bolts and receivers etc. but without the ability to practice on cheap receivers and the looser tolerances of the past etc., it is probably better to farm out such operations to professionals nowadays. Likewise, using cyanide compounds for heat treatment and arsenic compounds for bluing are not the most healthy of options even if you could get the chemicals to do such today. However, other formulas are presented as well and they date from a time that you could not simply buy the stuff off of the net from places like Brownells.
For many of us, we have been living in the era of abundance so long that we forget what scarcity in times like the Depression and post WWII were like. Books like these remind us that we may have more technology at our command but it has not necessarily made us wiser or even capable of doing things that our ancestors did without much thinking.