Yes, their work has value. There are good fundamental explanations in the encyclopedia for how spreads behaved at the time( although E Geman "Commodities and commodity derivatives" is better IMO ). It's just that the great bubble of 2008 and fund activity nowadays make their book obsolete.
FirstPoint, Of the three quasi-governmental softs organizations, The ICO (coffee) and ICCO (cocoa) release their supply & demand estimates and some other reports free to the public. The ISO (sugar) doesn't release squat for free and their prices are extremely high on a per-report basis. Fortunately, you can get the key ISO reports via www.sugaronline.com for $40/mo (Silver level membership, last time I looked). SugarOnline also gives you a 14-day free trial membership, which I think is pretty fair. The USDA dropped their quarterly "Tropical Products: World Markets and Trade" report several years ago but they still release twice-yearly global S&D estimates for coffee and sugar. I think they're out of the cocoa report business completely, although if you poke around the Foreign Agricultural Service (FAS) website you might find the occasional US agricultural attache report that mentions cocoa. Those are the free or low cost resources that I know of for S&D estimates on the softs. I catch the estimates out of Brasil in the news but I've never visited their Ministry of Agriculture or the various Brasil-based consultancy or trade association websites to see what they offer. If you're trading big time in the softs and money is no object, then firms like Judith Ganes Consulting and the long-established European traders/consultancies (Licht, Czarnikow, et.al.) generate a lot of S&D estimates and custom research.
The site http://www.agrimoney.com/ has news summaries of all major reports, including many research reports from trading firms, that may be adequate for most casual purposes.