A reader sent us this book for a look, and I'll start by offering the most important point: Lancaster does NOT say that we need to follow the Law to be saved or to even maintain salvation (eg, not a technical legalist, nor a covenantal nomist as Mormons are). He is rather like some Sabbatarians I know who regard it as a matter of conscience and devotion. There's nothing wrong with that.
However, when it comes to explaining why we SHOULD follow the Law, and what parts, Lancaster loses all semblance of rationality beyond an even, friendly (one may even say breathless) tone. Lancaster shows no sign of having any relevant credentials (it is not even said what credentials he does possess) and most of his sources come from the same well, a Hebraic Roots ministry (First Fruits of Zion). Lancaster spends much more time telling us how enjoyable it is to keep festivals than why we ought to. In the final analysis, his arguments amount to:
"Jesus and his followers kept the law, so we should too."
But what else would we expect if they lived in Judaea? What would we expect if they also ministered to Jews? A missionary to a Muslim village isn't going to eat pork.
The critical issue is whether Jewish-Christian missionaries told previously pagan converts to Christianity to obey the law, and on that point, Lancaster does a very poor job of arguing. The strictures of Acts 15, for example, he reads wrongly as prescription for following the law, when it is in fact prescription against attending pagan festivals.
"We still follow the laws of Torah even now."
It is true that we still consider many of the moral laws valid, and we have explained this as part of assessing categories of law. Lancaster is aware of this idea, but summarily and deficiently rejects it, based on an exceptionally literalist reading describing the Torah as "one law" in the OT (Num. 15:16 -- which doesn't say a thing about categories within that one law).
Ironically, while Lancaster admonishes against picking and choosing laws to follow, he does the same thing himself. He admits we can't do animal sacrifices without a Temple. Well, then, there can clearly be reasons not to follow other laws as well. Either we read the Torah like a fundamentalist or we contextualize it. Lancaster contextualizes when he finds it easy to do so but when it gets hard he retreats into defense mode. Not having a Temple is not a valid reply because we can build one and restart sacrifices. That someone may object is no argument either -- unless Lancaster admits that things can change about applying Torah, and once he does that, his case fully collapses. If the law is truly "eternal and unchanging" in the rigid way Lancaster suggests, then you can't ignore the law to build rails on your roof -- you have to do it, no matter what the reason was for it.
In the end, the laws Lancaster says we ought to obey (out of devotion) amount to keeping the Sabbath (addressed here). Lancaster does not even admit the force of the critical Col. 2:14-17 passages, or deal with it, aside from objecting that some versions put "mere" in the text and hypothesizing that the critics were those objecting that the Colossians followed the law without converting to Judaism -- which doesn't fit with the nature of the critics described in Colosse, as esoteric Judaizers.
On keeping of festivals, and keeping of diet laws: These he supports using questionable claims of better health benefits, which are passe' given modern sanitation practices. There are also other minor errors, such as Lancaster's claim that we all have an innate conscience [38] -- as anthropological scholarship shows, this is not the case. Likewise on the subject of ritual purity and what it was for, and how Christ has resolved those laws, as Paul had to explain to Peter.
Lancaster is someone who has allowed his convert's enthusiasm to overcome his better judgment, and he has presented no case for following the full law today. Keep it all of you want to, but it's not because you have to.
-JPH