While the formatting has an aesthetic goal, it misses the readability mark. Bodoni MT Black is a decorative font highly unsuitable for headlines and leads.

The layout between sections varies widely. The cramming of far too much information in the reference pages—aschewing all whitespace and using Bodoni MT Black again—piles on the formatting problems. Additionally, the page numbers are wildly off mark and restart or are left off. Where rooms have numerous items, long strings of italicized items, comma and semi-colon delimited, are used versus lists. This in part ties back to the extreme lack of whitespace.

1. Move all reference sheets to the end. It is unnecessary to append them to each section.
2. More whitespace.
3. More lists.
4. Consider also complete redo, but first read https://www.drivethrurpg.com/product/168306/A-Brief-Study-of-TSR-Book-Design. It's free even.
5. Fix the headers for each section/part; the header is missing on a number of pages
6. Fix the page numbers.

I - the buyer recently bought the T 1-4 with the intention of converting it to another iteration of the game. Basically, it was a matter of converting a conversion (i.e. a 3rd edition conversion on a forum somewhere was to be the basis for my then-converting it to Pathfinder). 5th addition then piqued my interest instead and I decided to capitalize on the existing conversion guides for that edition.

Now, I have no experience with 1st edition, or 2nd for that matter (outside of Baldur's Gate...) so as for how well this conversion guide carries over challenges from the original 1st edition to the environment of the 5th - I couldn't say. At least not before having tried it with my gaming group, but even then it will be a matter of adapting and improvising (i.e. 5 Monsters in that room of that variety may end up being 6.. etc). For anything to do with conversions, I am primarily looking - and hoping for - the ballpark.

It - the product does what it sets out to do, nothing more - nothing less. I am looking at 5th edition rules equivalents for nearly everything. Nearly, I say, because one big exception of course is monetary treasure. But this is more to do with how 5th treats coin than negligence on behalf of the author of the guide: with item prices given a range definition there is simply no way you are going to have a waterproof conversion of Farmer #15's stash of >1000 gp. And this is something you absolutely need to know if you are specifically on the hunt for that type of guidance: you are not going to get it here (either).

Magic item count? Well, it may or may not be in line with 5th, but it's a simple matter of removing the +X and then that's your toned-down sword of the treasure instead. There are guidelines provided for this very purpose too.

The DIY elements is not why the product only gets the 4 out of 5, however, because the meat here is nutritious and such.

Yes, there is a certain homebrew conversion guide which does a whole bunch of other things than just simply putting 5th edition labels on things. Personally, I abandonded that very conversion guide because it was over 100 pages and the layout had an awful lot to do with the page-count in an awful way - in my opinion. Yes, it had full stat blocks for certain NPC:s, and even some suggested sidequests (taken from the video game version), and expanded on the module itself in yet other ways (...that I wasn't necessarily looking for, but hey it was free). But. Layout. It's a thing, and in that particular case the extra goodness just did not make up for the poor presentation.

My 4/5 for this guide stems from presentation.

Now, it should be mentioned layout in this guide is - for the most part - functional and sound: Area -> Entry -> Replacement. BOOM! Rince and repeat. It's compact and you won't be flipping pages an awful lot.

The not-so-good bit is font incoherency and text colours. I don't know what the specific font used for the bold parts is called, but it absolutely requires some extra effort to read; not in the sense that it is unintelligible but it is simply too far apart from the rest of the text and that means one has to adjust to read it - which gets strenuous over time. It makes for good brochures and front-page stuff, perhaps, but in the text proper? Throw in a red header on top of that and you have one potent eye-buster cocktail!

If this is the template style of the product-line, then so be it: it's not something I would necessarily consider a dealbreaker but as far as finish is concerned - this certainly could be improved upon.

TLDR: The dish is good, but it's not a looker.

Very very basic conversion. It seems to only contain a simple creature MM 5e translation but without much in the way of difficulty adjustments. Very little updated on NPCs as an example. I didn't find this guide very helpful at all and was about the most basic of conversion guides possible.

Thankfully I later found Brian Rideout's T1-T4 5E conversion. That guide contains additional background material (researched based on the classic modules, associated video games, etc.), enhanced information on the story line to help the DM, quite a few great additional enounter ideas to improve the experience for everyone, and properly converted and balanced encounters (including NPCs).